[FLINK-38391][build] Bump maven-shade-plugin to 3.6.1 to support java 25

[snuyanzin]

What is the purpose of the change

bump maven-shade-plugin version

Brief change log

pom.xml

Verifying this change

This change is a trivial rework / code cleanup without any test coverage.

also could be verified by building with java25 target

Does this pull request potentially affect one of the following parts:

• Dependencies (does it add or upgrade a dependency): (yes )
• The public API, i.e., is any changed class annotated with @Public(Evolving): ( no)
• The serializers: ( no)
• The runtime per-record code paths (performance sensitive): ( no)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: ( no)
• The S3 file system connector: (no )

Documentation

• Does this pull request introduce a new feature? ( no)
• If yes, how is the feature documented? (not applicable )

[flinkbot]

CI report:

• 701a0a6 Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

• @flinkbot run azure re-run the last Azure build