Remove a default value

See https://github.com/pytest-dev/pytest/pull/11901\#discussion_r1473038296

Author: Pierre-Sassoulas

pyproject.toml

@@ -135,4 +135,3 @@ force-single-line = true
 known-local-folder = ["pytest", "_pytest"]
 known-third-party = ["test_source", "test_excinfo"]
 force-sort-within-sections = true
-case-sensitive = false