[refurb] Mark fix as safe for readlines-in-for (FURB129)

[dylwil3]

This PR promotes the fix applicability of readlines-in-for (FURB129) to always safe.

In the original PR (#9880), the author marked the rule as unsafe because Ruff's type inference couldn't quite guarantee that we had an IOBase object in hand. Some false positives were recorded in the test fixture. However, before the PR was merged, Charlie added the necessary type inference and the false positives went away.

According to the Python documentation, I believe this fix is safe for any proper implementation of IOBase:

IOBase (and its subclasses) supports the iterator protocol, meaning that an IOBase object can be iterated over yielding the lines in a stream. Lines are defined slightly differently depending on whether the stream is a binary stream (yielding bytes), or a text stream (yielding character strings). See readline() below.

and then in the documentation for readlines:

Read and return a list of lines from the stream. hint can be specified to control the number of lines read: no more lines will be read if the total size (in bytes/characters) of all lines so far exceeds hint. [...]
Note that it’s already possible to iterate on file objects using for line in file: ... without calling file.readlines().

I believe that a careful reading of our versioning policy requires that this change be deferred to a minor release - but please correct me if I'm wrong!

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

ℹ️ ecosystem check detected linter changes. (+0 -0 violations, +10 -0 fixes in 1 projects; 54 projects unchanged)

apache/airflow (+0 -0 violations, +10 -0 fixes)

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

- dev/airflow_perf/sql_queries.py:145:41: FURB129 Instead of calling `readlines()`, iterate over file object directly
+ dev/airflow_perf/sql_queries.py:145:41: FURB129 [*] Instead of calling `readlines()`, iterate over file object directly
- dev/breeze/src/airflow_breeze/global_constants.py:553:21: FURB129 Instead of calling `readlines()`, iterate over file object directly
+ dev/breeze/src/airflow_breeze/global_constants.py:553:21: FURB129 [*] Instead of calling `readlines()`, iterate over file object directly
- devel-common/src/sphinx_exts/redirects.py:44:21: FURB129 Instead of calling `readlines()`, iterate over file object directly
+ devel-common/src/sphinx_exts/redirects.py:44:21: FURB129 [*] Instead of calling `readlines()`, iterate over file object directly
- providers/google/tests/system/google/cloud/gcs/resources/transform_script.py:26:39: FURB129 Instead of calling `readlines()`, iterate over file object directly
+ providers/google/tests/system/google/cloud/gcs/resources/transform_script.py:26:39: FURB129 [*] Instead of calling `readlines()`, iterate over file object directly
- scripts/ci/pre_commit/newsfragments.py:36:43: FURB129 Instead of calling `readlines()`, iterate over file object directly
+ scripts/ci/pre_commit/newsfragments.py:36:43: FURB129 [*] Instead of calling `readlines()`, iterate over file object directly

Changes by rule (1 rules affected)

code	total	+ violation	- violation	+ fix	- fix
FURB129	10	0	0	10	0

[MichaReiser]

This sounds reasonable to me. Yes, I think this needs to be gated behind preview