[FLINK-37249] Remove unnecessary --add-opens/--add-exports for java.base/sun.net.util

[X-czh]

What is the purpose of the change

-add-opens/-add-exports for java.base/sun.net.util was added in FLINK-25002, but was no longer necessary after FLINK-30478 is merged. We should remove it to simplify the build system.

Brief change log

Remove unnecessary --add-opens/--add-exports for java.base/sun.net.util.

Verifying this change

Verified by compiling wand running locally with JDK17.

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

• Dependencies (does it add or upgrade a dependency): (yes / no)
• The public API, i.e., is any changed class annotated with @Public(Evolving): (yes / no)
• The serializers: (yes / no / don't know)
• The runtime per-record code paths (performance sensitive): (yes / no / don't know)
• Anything that affects deployment or recovery: JobManager (and its components), Checkpointing, Kubernetes/Yarn, ZooKeeper: (yes / no / don't know)
• The S3 file system connector: (yes / no / don't know)

Documentation

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

[flinkbot]

CI report:

• ceb878d Azure: SUCCESS

Bot commands

The @flinkbot bot supports the following commands:

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

[X-czh]

Hi @zentol, would you be willing to take a review?