gh-148427: Revert finally clause, remove stack assertion

Drop the finally clause per reviewer feedback — the stack cleanup
behavior change is a separate concern. Remove the entity stack
assertion that depended on it.

Author: WYSIATI

Lib/test/test_sax.py

@@ -1078,7 +1078,6 @@ def raise_on_entity(name, attrs):
 
         if issubclass(exc_type, Exception):
             self.assertRaises(SAXParseException, parser.feed, trigger)
-            self.assertEqual(len(parser._entity_stack), 0)
         else:
             with self.assertRaisesRegex(exc_type, "test"):
                 parser.feed(trigger)

Lib/xml/sax/expatreader.py

@@ -426,9 +426,9 @@ def external_entity_ref(self, context, base, sysid, pubid):
             xmlreader.IncrementalParser.parse(self, source)
         except Exception:
             return 0  # FIXME: save error info here?
-        finally:
-            (self._parser, self._source) = self._entity_stack[-1]
-            del self._entity_stack[-1]
+
+        (self._parser, self._source) = self._entity_stack[-1]
+        del self._entity_stack[-1]
         return 1
 
     def skipped_entity_handler(self, name, is_pe):