Update Documentation to Specify Java 8 for Maven Builds

[Annaseli]

When running make test with Maven using Java 23, the following error occurs:

[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  1.770 s
[INFO] Finished at: 2025-01-28T17:43:16+02:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.8.1:testCompile (default-testCompile) on project hadoop-lakefs: Compilation failure: Compilation failure: 
[ERROR] /Users/annaseliverstov/work/lakeFS/clients/hadoopfs/src/test/java/io/lakefs/FSTestBase.java:[320,57] cannot find symbol
[ERROR]   symbol:   class ImmutablePagination
[ERROR]   location: class io.lakefs.FSTestBase
[ERROR] /Users/annaseliverstov/work/lakeFS/clients/hadoopfs/src/test/java/io/lakefs/FSTestBase.java:[324,68] cannot find symbol
[ERROR]   symbol:   class ImmutablePagination
[ERROR]   location: class io.lakefs.FSTestBase

The failure occurs in the hadoopfs client tests. However, when using Java 8, the tests pass successfully.

Proposed Fix:

1. Update the lakeFS Contributing Guide

   • Under Setting up an Environment, in the section on Maven, specify that Java 8 is required for building and testing the hadoopfs client.

2. Update the README in clients/hadoopfs

   • Add a building section stating that Maven tests should be run with Java 8.