Maven is configured to use the wrong Java version for 4.x

[shawjef3]

.github/4.x-release.yml has java-version: '21', but pom.xml has <maven.compiler.source>1.8</maven.compiler.source>. This causes local build failures. Instead, the pom should be the following, which matches the github build.

<maven.compiler.source>21</maven.compiler.source>
<maven.compiler.target>21</maven.compiler.target>

[lamrowena]

@iabmayank can you take a look at this?

[iabmayank]

yes let me work on this @lamrowena fix and update this