[ZEPPELIN-6477] Stop dumping stack trace on Groovy cancellation

[vividbaek]

What is this PR for?

Remove the Thread.dumpStack() call from Groovy paragraph cancellation because it writes an unnecessary stack trace directly to stderr.

The existing t.interrupt() call is preserved, so the paragraph cancellation behavior remains unchanged.

What type of PR is it?

Improvement

Todos

• Remove the unnecessary stack dump
• Preserve the thread interruption behavior
• Run the Groovy module build and tests

What is the Jira issue?

https://issues.apache.org/jira/browse/ZEPPELIN-6477

How should this be tested?

./mvnw test -pl groovy

The build completed successfully.

Screenshots (if appropriate)

Not applicable.

Questions:

• Does the license files need to update? No
• Is there breaking changes for older versions? No
• Does this needs documentation? No

[tbonelee]

LGTM.

For the record: Thread.dumpStack() is static, so t.dumpStack() printed the cancelling thread's stack to stderr, not the cancelled one's. No diagnostic value, and it bypassed the logger. t.interrupt() does the real work and is untouched.