logging: drop an unreachable guard in the stale-snapshot test

The key is asserted present just above and nothing removes it while the
handler is alive, so the 'if key in cache' branch could never be False.
Codecov counted it as a partial branch; removing it makes the file's patch
coverage exact.

Author: DawnofGenX

testing/logging/test_bound_proxy.py

@@ -1071,10 +1071,11 @@ def test_stale_cache_entry_is_rejected_via_the_back_reference() -> None:
         # ``other`` may or may not be cached under a different key; what must
         # hold is that the original snapshot can no longer validate: its
         # back-reference would not resolve to whichever handler looks it up.
-        if key in catching_logs._target_cache:
-            entry = catching_logs._target_cache[key]
-            assert entry.handler_ref is stale_ref
-            assert entry.handler_ref() is handler  # still alive here
+        # The entry for ``handler`` is still present (asserted above and not
+        # evicted while ``handler`` is alive), so no guard is needed here.
+        entry = catching_logs._target_cache[key]
+        assert entry.handler_ref is stale_ref
+        assert entry.handler_ref() is handler  # still alive here
 
     # Once the handler is really gone, the back-reference resolves to nothing
     # and the entry can never pass the ``handler_ref() is handler`` check.