Fix CI upstream tests

Remove unnecessary 'gem' packaging during upstream gem installation.

* Bump jruby used for gem installation to 9.2.21.0

CHANGELOG.adoc

@@ -13,6 +13,10 @@ For a detailed view of what has changed, refer to the {url-repo}/commits/main[co
 
 == Unreleased
 
+Build / Infrastructure::
+
+* Fix Asciidoctor upstream CI tests (#1178) (@abelsromero)
+
 == 2.5.8 (2023-04-15)
 
 Improvement::

ci/asciidoctor-gem-installer.pom

@@ -5,10 +5,9 @@
     <groupId>rubygems</groupId>
     <artifactId>asciidoctor</artifactId>
     <version></version>
-    <packaging>gem</packaging>
     <name>Asciidoctor RubyGem Installer</name>
     <description>Installs the upstream Asciidoctor RubyGem to the local repository.</description>
-    <url>http://asciidoctor.org</url>
+    <url>https://asciidoctor.org</url>
     <repositories>
         <repository>
             <id>rubygems-releases</id>

ci/test-asciidoctor-upstream.sh

@@ -26,7 +26,10 @@ sed "s;<version></version>;<version>$ASCIIDOCTOR_VERSION</version>;" pom.xml > p
   mv -f pom.xml.sedtmp pom.xml
 
 # we override the jruby version here with one supported by java9, additionally java9 needs some add-opens arguments that need to be ignored on older jvms
-mvn install -B --no-transfer-progress -Dgemspec=asciidoctor.gemspec -Djruby.version=9.2.17.0 -Djruby.jvmargs="-XX:+IgnoreUnrecognizedVMOptions --add-opens=java.base/java.security.cert=ALL-UNNAMED --add-opens=java.base/java.security=ALL-UNNAMED --add-opens=java.base/java.util.zip=ALL-UNNAMED"
+mvn install -B --no-transfer-progress \
+  -Dgemspec=asciidoctor.gemspec \
+  -Djruby.version=9.2.21.0 \
+  -Djruby.jvmargs="-XX:+IgnoreUnrecognizedVMOptions --add-opens=java.base/java.security.cert=ALL-UNNAMED --add-opens=java.base/java.security=ALL-UNNAMED --add-opens=java.base/java.util.zip=ALL-UNNAMED"
 popd
 
 ## Test against installed gem