Do not test on Java 25 and 26

Experiencing some JVM crashes with the C2 compiler (on Netty classes).
Disabling for now to investigate unrelated flakes.

Author: acogoluegnes

.github/workflows/test-pr.yml

@@ -20,7 +20,7 @@ jobs:
         uses: actions/setup-java@v5
         with:
           distribution: 'temurin'
-          java-version: '25'
+          java-version: '21'
           cache: 'maven'
       - name: Start broker
         run: ci/start-broker.sh

.github/workflows/test-rabbitmq-alphas.yml

@@ -28,7 +28,7 @@ jobs:
         uses: actions/setup-java@v5
         with:
           distribution: 'temurin'
-          java-version: '25'
+          java-version: '21'
           cache: 'maven'
       - name: Start broker
         run: ci/start-broker.sh

.github/workflows/test-supported-java-versions.yml

@@ -11,10 +11,7 @@ jobs:
     strategy:
       matrix:
         distribution: [ 'temurin' ]
-        version: [ '11', '17', '21', '25', '26-ea' ]
-        include:
-          - distribution: 'semeru'
-            version: '17'
+        version: [ '11', '17', '21' ]
     name:  Test against Java ${{ matrix.distribution }} ${{ matrix.version }}
     steps:
       - uses: actions/checkout@v5

.github/workflows/test.yml

@@ -21,7 +21,7 @@ jobs:
         uses: actions/setup-java@v5
         with:
           distribution: 'temurin'
-          java-version: '25'
+          java-version: '21'
           cache: 'maven'
           server-id: central
           server-username: MAVEN_USERNAME