Also build using the selected Java version

build.gradle

@@ -41,8 +41,6 @@ group = "org.jabref"
 version = project.findProperty('projVersion') ?: '100.0.0'
 
 java {
- sourceCompatibility = JavaVersion.VERSION_21
- targetCompatibility = JavaVersion.VERSION_21
  // Workaround needed for Eclipse, probably because of https://github.com/gradle/gradle/issues/16922
  // Should be removed as soon as Gradle 7.0.1 is released ( https://github.com/gradle/gradle/issues/16922#issuecomment-828217060 )
  modularity.inferModulePath.set(false)
@@ -51,6 +49,7 @@ java {
  // If this is updated, also update
  // - .devcontainer/devcontainer.json#L34 and
  // - .gitpod.Dockerfile
+ // This setting also sets sourceCompatibility and targetCompatibility
  languageVersion = JavaLanguageVersion.of(21)
  }
 }