python3-propcache: Drop the PEP 517 backend test from ptests

tests/test_pep517_backend.py imports the in-tree build backend from
packaging/pep517_backend, which pytest.ini puts on the path when run
from the source tree but which is not installed. Collection fails and
pytest stops without running any test:

  E   ModuleNotFoundError: No module named 'pep517_backend'

The test checks the CFLAGS/CPPFLAGS handling of the build backend,
which has no use on the target, so remove it.

AI-Generated: Uses Claude Code
Signed-off-by: Khem Raj <khem.raj@oss.qualcomm.com>

meta-python/recipes-devtools/python/python3-propcache_0.5.4.bb

@@ -21,4 +21,9 @@ RDEPENDS:${PN}-ptest += " \
 	python3-statistics \
 "
 
+do_install_ptest:append() {
+	# tests the in-tree build backend, which is not installed
+	rm -f ${D}${PTEST_PATH}/tests/test_pep517_backend.py
+}
+
 BBCLASSEXTEND += "native nativesdk"