testing/py3-fastapi: remove leftover file

testing/py3-fastapi/pytest-markers.patch

---- a/pyproject.toml
-+++ b/pyproject.toml
-@@ -90,6 +90,9 @@
-   "--strict-markers",
-   "--ignore=docs_src",
- ]
-+markers = [
-+  "filterwarnings",
-+]
- xfail_strict = true
- junit_family = "xunit2"
- filterwarnings = [