CI: Install JRuby 10 w/ Java 21 & JRuby 9 w/ Java 17

Without Java 10, JRuby 10.0.5.0 gives us:

```
  attempting to run with existing JAVA_HOME
  /usr/lib/jvm/temurin-17-jdk-amd64/bin/java -jar /home/runner/.rubies/jruby-10.0.5.0/lib/jruby.jar --version
  Error: LinkageError occurred while loading main class org.jruby.main.Main
        java.lang.UnsupportedClassVersionError: org/jruby/main/Main has been compiled by a more recent version of the Java Runtime (class file version 65.0), this version of the Java Runtime only recognizes class file versions up to 61.0
  JRuby failed to start, try Java 21 envs
  Setting JAVA_HOME to JAVA_HOME_21_X64 path /usr/lib/jvm/temurin-21-jdk-amd64
  Adding /usr/lib/jvm/temurin-21-jdk-amd64/bin to PATH
  Took   0.24 seconds
```

Signed-off-by: Tim Meusel <tim@bastelfreak.de>

Author: bastelfreak

.github/workflows/ci.yaml

@@ -44,7 +44,20 @@ jobs:
     steps:
       - name: Checkout current PR
         uses: actions/checkout@v6
-
+      # we explictly force Java 17 because that's the lowest one we support when building packages with ezbake
+      - name: Set up Java 17 for JRuby 9
+        if: contains(matrix.ruby, 'jruby-9')
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '17'
+      # JRuby 10.0.5 requires java 21 or 25
+      - name: Set up Java 21 for JRuby 10
+        if: contains(matrix.ruby, 'jruby-10')
+        uses: actions/setup-java@v4
+        with:
+          distribution: temurin
+          java-version: '21'
       - name: Rspec checks
         uses: ruby/setup-ruby@v1
         with: