Mark test_request_garbage as flaky on Windows

#3564

Author: nicoddemus

testing/python/fixture.py

@@ -1,3 +1,4 @@
+import sys
 from textwrap import dedent
 
 import _pytest._code
@@ -625,6 +626,9 @@ def test_method(self, something):
         assert len(arg2fixturedefs) == 1
         assert arg2fixturedefs["something"][0].argname == "something"
 
+    @pytest.mark.xfail(
+        sys.platform.startswith("win"), reason="flaky on Windows (#3564)"
+    )
     def test_request_garbage(self, testdir):
         testdir.makepyfile(
             """