Use Java 24 for running Gradle

As of Gradle 8.14, Gradle is now compatible with Java 24 for running
Gradle.

Author: bclozel

.github/actions/prepare-gradle-build/action.yml

@@ -19,7 +19,7 @@ inputs:
   java-version:
     description: 'Java version to use for the build'
     required: false
-    default: '17'
+    default: '24'
 runs:
   using: composite
   steps: