fix: ensure PC191 doesn't trigger for flake8

Signed-off-by: Henry Schreiner <henryfs@princeton.edu>

Author: henryiii

src/sp_repo_review/checks/precommit.py

@@ -173,8 +173,7 @@ def check(  # type: ignore[override]
                         return "--show-fixes" in hook["args"] or (
                             ruff is not None and "show-fixes" in ruff
                         )
-                return None
-        return False
+        return None
 
 
 class PC192(PreCommit):

tests/test_precommit.py

@@ -246,6 +246,15 @@ def test_pc191_no_show_fixes(ruff_check: str, ruffconfig):
     assert "--show-fixes" in res.err_msg
 
 
+def test_pc191_no_ruff():
+    precommit = yaml.safe_load("""
+        repos:
+          - repo: https://github.com/pycqa/flake8
+    """)
+    res = compute_check("PC191", precommit=precommit, ruff={})
+    assert res.result is None
+
+
 def test_pc192():
     precommit = yaml.safe_load("""
         repos: