Apply suggestion from @picnixz

Registered the cache cleanup via addCleanup to keep the test environment isolated.

Co-authored-by: Bénédikt Tran <10796600+picnixz@users.noreply.github.com>

Author: Bolotnyj

Lib/test/test_filecmp.py

@@ -82,6 +82,7 @@ def test_cache_clear(self):
 
     def test_cache_overflow_and_hit(self):
         filecmp.clear_cache()
+        self.addCleanup(filecmp.clear_cache)
         s1 = filecmp._sig(os.stat(self.name))
         s2 = filecmp._sig(os.stat(self.name_same))
         base_dir = os.path.dirname(self.name)