Use required Java version in CI

Attempt to fix this build issue on Windows:

```
What went wrong:
Execution failed for task ':compileJava'.
> Error while evaluating property 'javaCompiler' of task ':compileJava'.
   > Failed to calculate the value of task ':compileJava' property 'javaCompiler'.
      > Cannot find a Java installation on your machine matching this tasks requirements: {languageVersion=11, vendor=any, implementation=vendor-specific} for WINDOWS on x86_64.
         > No locally installed toolchains match and toolchain download repositories have not been configured.
```

.github/workflows/build.yml

@@ -25,7 +25,7 @@ jobs:
       - uses: actions/setup-java@v4
         with:
           distribution: "temurin"
-          java-version: "21"
+          java-version: "11"
 
       - name: Build with Gradle
         run: ./gradlew build --no-daemon