Remove unnecessary whitespace in slice notation to align with PEP 8 and Black standards

[michaelwlin-osu]

File: flask/src/flask/cli.py
Line: 701

The return statement in the _path_is_ancestor function can be updated to improve readability and align with PEP 8 and Black formatting standards for slice notation. Currently, there is unnecessary whitespace around the colon (:) in the slice, which is inconsistent with these guidelines.

Current Code:
return os.path.join(path, other[len(path) :].lstrip(os.sep)) == other

Suggested Change:
Remove the unnecessary whitespace around the colon (:) in the slice notation to improve readability:
return os.path.join(path, other[len(path):].lstrip(os.sep)) == other

This change ensures compliance with PEP 8 and Black standards, contributing to cleaner and more consistent formatting across the codebase.

[ThiefMaster]

Please don't open issues/PRs related to formatting.