[JarryShaw]

• Searched for similar pull requests

• Followed the coding style (make pylint, make mypy, make isort)

• make test passes, and a test case covers the change — deletes a dead cleanup, so there is no new test; test_mh_unit passes alone and alongside tests/utilities

• Added a changelog entry — N/A — centralised in docs(changelog): shared 1.5.0 changelog — long-lived, merges last (#610, #616, #617, #618, #620) #657

• test — tests only

This drops test_mh_unit's _drop_tracebacklimit cleanup and the import sys that only it used. Since #362, no pcapkit code sets sys.tracebacklimit: git grep finds only docstrings. The cleanup also deleted the attribute whenever it existed, which would remove a value the test runner had set. The test files that do touch sys.tracebacklimit save and restore it themselves.

Closes #1924

[JarryShaw]

GOOD TO GO at 66c87dc71. A Sonnet cross-review read every tracebacklimit hit in pcapkit/. All five are prose in utilities/exceptions.py, and the trim rule goes through tbtrim, which never touches it. sys has no other use in the method. test_mh_unit.py passes run before and run after the files that do set sys.tracebacklimit (227 passed in each order). The commit is the one 13-line deletion.