Switch GH ci action to Java 21

Moves the org.eclipse.jdt.core.tests.builder profile to Java 21 too so
it keeps getting tested as there were no newer profiles in this bundle.

.github/workflows/ci.yml

@@ -43,7 +43,7 @@ jobs:
     - name: Build with Maven 🏗️
       run: |
         mvn clean install --batch-mode -f org.eclipse.jdt.core.compiler.batch -DlocalEcjVersion=99.99
-        mvn -U clean verify --batch-mode --fail-at-end -Ptest-on-javase-20 -Pbree-libs -Papi-check -Djava.io.tmpdir=$WORKSPACE/tmp -Dproject.build.sourceEncoding=UTF-8 -Dtycho.surefire.argLine="--add-modules ALL-SYSTEM -Dcompliance=1.8,11,17,20 -Djdt.performance.asserts=disabled" -Dcbi-ecj-version=99.99
+        mvn -U clean verify --batch-mode --fail-at-end -Ptest-on-javase-21 -Pbree-libs -Papi-check -Djava.io.tmpdir=$WORKSPACE/tmp -Dproject.build.sourceEncoding=UTF-8 -Dtycho.surefire.argLine="--add-modules ALL-SYSTEM -Dcompliance=1.8,11,17,20 -Djdt.performance.asserts=disabled" -Dcbi-ecj-version=99.99
     - name: Upload Test Results for Linux
       if: always()
       uses: actions/upload-artifact@5d5d22a31266ced268874388b861e4b58bb5c2f3 # v4.3.1

org.eclipse.jdt.core.tests.builder/pom.xml

@@ -64,7 +64,7 @@
 		</properties>
 	</profile>
 	<profile>
-		<id>test-on-javase-20</id>
+		<id>test-on-javase-21</id>
 		<build>
 			<plugins>
 				<plugin>
@@ -73,15 +73,15 @@
 					<configuration>
 						<toolchains>
 							<jdk>
-								<id>JavaSE-20</id>
+								<id>JavaSE-21</id>
 							</jdk>
 						</toolchains>
 					</configuration>
 				</plugin>
 			</plugins>
 		</build>
 		<properties>
-			<tycho.surefire.argLine>--add-modules ALL-SYSTEM -Dcompliance=1.4,1.7,1.8,20</tycho.surefire.argLine>
+			<tycho.surefire.argLine>--add-modules ALL-SYSTEM -Dcompliance=1.4,1.7,1.8,21</tycho.surefire.argLine>
 		</properties>
 	</profile>
   </profiles>