Bump slimmer from 13.2.0 to 13.2.2

Bumps [slimmer](https://github.com/alphagov/slimmer) from 13.2.0 to 13.2.2.
- [Release notes](https://github.com/alphagov/slimmer/releases)
- [Changelog](https://github.com/alphagov/slimmer/blob/master/CHANGELOG.md)
- [Commits](alphagov/slimmer@v13.2.0...v13.2.2)

Signed-off-by: dependabot-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

Gemfile.lock

@@ -140,7 +140,7 @@ GEM
       phantomjs (>= 1.9)
       railties (>= 3.2.0)
       sprockets-rails
-    json (2.2.0)
+    json (2.3.0)
     json-schema (2.8.1)
       addressable (>= 2.4)
     kgio (2.11.3)
@@ -294,7 +294,7 @@ GEM
       rubyzip (>= 1.2.2)
     sentry-raven (2.13.0)
       faraday (>= 0.7.6, < 1.0)
-    slimmer (13.2.0)
+    slimmer (13.2.2)
       activesupport
       json
       nokogiri (~> 1.7)