Normalize alpm md5 refs

[wagoodman]

Small fix to normalize the md5digest references to simply md5 like with other catalogers that raise up digests with algorithm references.

[github-actions]

Benchmark Test Results

Benchmark results from the latest changes vs base branch

name                                                       old time/op    new time/op    delta
ImagePackageCatalogers/alpmdb-cataloger-2                    11.3ms ± 0%    12.0ms ±14%  +6.65%  (p=0.016 n=4+5)
ImagePackageCatalogers/ruby-gemspec-cataloger-2              1.26ms ± 1%    1.33ms ± 5%  +5.59%  (p=0.008 n=5+5)
ImagePackageCatalogers/python-package-cataloger-2            3.25ms ± 1%    3.29ms ± 1%    ~     (p=0.095 n=5+5)
ImagePackageCatalogers/php-composer-installed-cataloger-2    1.04ms ± 0%    1.07ms ± 1%  +3.51%  (p=0.008 n=5+5)
ImagePackageCatalogers/javascript-package-cataloger-2         717µs ± 0%     752µs ± 1%  +4.96%  (p=0.008 n=5+5)
ImagePackageCatalogers/node-binary-cataloger-2               6.67µs ± 1%    6.50µs ± 0%  -2.55%  (p=0.016 n=5+4)
ImagePackageCatalogers/dpkgdb-cataloger-2                     826µs ± 1%     875µs ± 1%  +5.92%  (p=0.008 n=5+5)
ImagePackageCatalogers/rpm-db-cataloger-2                    1.19ms ± 1%    1.29ms ± 1%  +8.05%  (p=0.008 n=5+5)
ImagePackageCatalogers/java-cataloger-2                      14.1ms ± 0%    14.7ms ± 1%  +4.39%  (p=0.008 n=5+5)
ImagePackageCatalogers/apkdb-cataloger-2                     1.22ms ± 1%    1.29ms ± 3%  +5.84%  (p=0.008 n=5+5)
ImagePackageCatalogers/go-module-binary-cataloger-2          6.73µs ± 1%    6.60µs ± 1%  -1.91%  (p=0.008 n=5+5)
ImagePackageCatalogers/dotnet-deps-cataloger-2               1.34ms ± 2%    1.39ms ± 2%  +3.98%  (p=0.008 n=5+5)
ImagePackageCatalogers/portage-cataloger-2                    669µs ± 0%     722µs ± 1%  +7.99%  (p=0.008 n=5+5)

name                                                       old alloc/op   new alloc/op   delta
ImagePackageCatalogers/alpmdb-cataloger-2                    5.27MB ± 0%    5.26MB ± 0%    ~     (p=0.222 n=5+5)
ImagePackageCatalogers/ruby-gemspec-cataloger-2               205kB ± 0%     205kB ± 0%    ~     (p=0.151 n=5+5)
ImagePackageCatalogers/python-package-cataloger-2             963kB ± 0%     962kB ± 0%  -0.18%  (p=0.008 n=5+5)
ImagePackageCatalogers/php-composer-installed-cataloger-2     218kB ± 0%     218kB ± 0%    ~     (p=0.095 n=5+5)
ImagePackageCatalogers/javascript-package-cataloger-2         159kB ± 0%     159kB ± 0%  -0.09%  (p=0.032 n=5+5)
ImagePackageCatalogers/node-binary-cataloger-2               1.12kB ± 0%    1.12kB ± 0%    ~     (all equal)
ImagePackageCatalogers/dpkgdb-cataloger-2                     200kB ± 0%     200kB ± 0%  -0.10%  (p=0.008 n=5+5)
ImagePackageCatalogers/rpm-db-cataloger-2                     303kB ± 0%     303kB ± 0%  -0.15%  (p=0.008 n=5+5)
ImagePackageCatalogers/java-cataloger-2                      3.45MB ± 0%    3.45MB ± 0%    ~     (p=0.690 n=5+5)
ImagePackageCatalogers/apkdb-cataloger-2                     1.26MB ± 0%    1.25MB ± 0%  -0.12%  (p=0.008 n=5+5)
ImagePackageCatalogers/go-module-binary-cataloger-2          1.12kB ± 0%    1.12kB ± 0%    ~     (all equal)
ImagePackageCatalogers/dotnet-deps-cataloger-2                376kB ± 0%     376kB ± 0%    ~     (p=0.421 n=5+5)
ImagePackageCatalogers/portage-cataloger-2                    139kB ± 0%     139kB ± 0%    ~     (p=0.254 n=5+5)

name                                                       old allocs/op  new allocs/op  delta
ImagePackageCatalogers/alpmdb-cataloger-2                     85.7k ± 0%     85.7k ± 0%    ~     (p=0.413 n=5+4)
ImagePackageCatalogers/ruby-gemspec-cataloger-2               4.26k ± 0%     4.26k ± 0%    ~     (all equal)
ImagePackageCatalogers/python-package-cataloger-2             16.6k ± 0%     16.6k ± 0%    ~     (p=0.651 n=5+5)
ImagePackageCatalogers/php-composer-installed-cataloger-2     5.53k ± 0%     5.53k ± 0%    ~     (p=0.365 n=5+5)
ImagePackageCatalogers/javascript-package-cataloger-2         3.33k ± 0%     3.33k ± 0%    ~     (all equal)
ImagePackageCatalogers/node-binary-cataloger-2                 38.0 ± 0%      38.0 ± 0%    ~     (all equal)
ImagePackageCatalogers/dpkgdb-cataloger-2                     4.51k ± 0%     4.51k ± 0%    ~     (all equal)
ImagePackageCatalogers/rpm-db-cataloger-2                     8.13k ± 0%     8.13k ± 0%    ~     (all equal)
ImagePackageCatalogers/java-cataloger-2                       57.5k ± 0%     57.5k ± 0%    ~     (p=0.079 n=5+5)
ImagePackageCatalogers/apkdb-cataloger-2                      5.39k ± 0%     5.39k ± 0%  -0.02%  (p=0.016 n=4+5)
ImagePackageCatalogers/go-module-binary-cataloger-2            38.0 ± 0%      38.0 ± 0%    ~     (all equal)
ImagePackageCatalogers/dotnet-deps-cataloger-2                7.24k ± 0%     7.24k ± 0%    ~     (all equal)
ImagePackageCatalogers/portage-cataloger-2                    3.59k ± 0%     3.58k ± 0%    ~     (p=0.167 n=5+5)