[flake8-bugbear] Remove misleading multiple characters in lstrip

See https://pylint.readthedocs.io/en/stable/user_guide/messages/error/bad-str-strip-call.html

pyproject.toml

@@ -140,7 +140,6 @@ select = [
 ignore = [
     # bugbear ignore
     "B004", # Using `hasattr(x, "__call__")` to test if x is callable is unreliable.
-    "B005", # Using `.strip()` with multi-character strings is misleading
     "B006", # Do not use mutable data structures for argument defaults
     "B007", # Loop control variable `i` not used within loop body
     "B009", # Do not call `getattr` with a constant attribute value

testing/test_warnings.py

@@ -18,8 +18,7 @@ WARNINGS_SUMMARY_HEADER = "warnings summary"
 def pyfile_with_warnings(pytester: Pytester, request: FixtureRequest) -> str:
     """Create a test file which calls a function in a module which generates warnings."""
     pytester.syspathinsert()
-    test_name = request.function.__name__
-    module_name = test_name.lstrip("test_") + "_module"
+    module_name = request.function.__name__[len("test_") :] + "_module"
     test_file = pytester.makepyfile(
         f"""
         import {module_name}