[ruff 0.8] [flake8-pytest-style] Remove deprecated rules PT004 and PT005

[AlexWaygood]

Summary

Remove PT004 and PT005. These were deprecated in #12837, which landed as part of Ruff 0.6 (released on August 15th). There are no open issues on the tracker asking us to undeprecate them.

Test Plan

• cargo test
• git grep PytestMissingFixtureNameUnderscore, git grep PytestIncorrectFixtureNameUnderscore, git grep PT004 and git grep PT005 all show no results
• Wait to see what the ecosystem report looks like

[github-actions]

ruff-ecosystem results

Linter (stable)

ℹ️ ecosystem check detected linter changes. (+1 -3 violations, +0 -0 fixes in 2 projects; 52 projects unchanged)

freedomofpress/securedrop (+1 -0 violations, +0 -0 fixes)

+ molecule/testinfra/ossec/test_journalist_mail.py:14:45: RUF100 [*] Unused `noqa` directive (non-enabled: `PT004`)

rotki/rotki (+0 -3 violations, +0 -0 fixes)

- rotkehlchen/tests/fixtures/globaldb.py:207:5: PT004 Fixture `fixture_historical_price_test_data` does not return anything, add leading underscore
- rotkehlchen/tests/fixtures/oracles.py:20:5: PT004 Fixture `fixture_cache_coinlist` does not return anything, add leading underscore
- rotkehlchen/tests/fixtures/thegraph.py:13:5: PT004 Fixture `fixture_add_subgraph_api_key` does not return anything, add leading underscore

Changes by rule (2 rules affected)

code	total	+ violation	- violation	+ fix	- fix
PT004	3	0	3	0	0
RUF100	1	1	0	0	0

Linter (preview)

✅ ecosystem check detected no linter changes.

[AlexWaygood]

Ecosystem report analysis:

• The freedomofpress and rotki codebases see a few errors going away as a result of these removals.
• All other hits are TOML parse errors due to the fact that various repos had the rules explicitly ignored before now (which feels like it validates the choice to remove these rules)

[AlexWaygood]

Same concern as #14384 (comment) about merging this now...