[syntax-errors] Fix false positive for parenthesized tuple index

[ntBre]

Summary

Fixes #16943 by checking if the tuple is not parenthesized before emitting an error.

Test Plan

New inline test based on the initial report

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+0 -2 violations, +0 -0 fixes in 1 projects; 54 projects unchanged)

mesonbuild/meson-python (+0 -2 violations, +0 -0 fixes)

ruff check --no-cache --exit-zero --ignore RUF9 --no-fix --output-format concise --preview

- mesonpy/_editable.py:253:31: SyntaxError: Cannot use star expression in index on Python 3.8 (syntax was added in Python 3.11)
- mesonpy/_editable.py:253:48: SyntaxError: Cannot use star expression in index on Python 3.8 (syntax was added in Python 3.11)

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
SyntaxError:	2	0	2	0	0

Formatter (stable)

✅ ecosystem check detected no format changes.

Formatter (preview)

✅ ecosystem check detected no format changes.