refactor: Remove "subject" from stream_topic.py.

tools/linter_lib/custom_check.py

@@ -37,11 +37,6 @@ FILES_WITH_LEGACY_SUBJECT = {
     # These are tied more to our API than our DB model.
     'zerver/lib/api_test_helpers.py',
 
-    # TRY TO FIX THESE! If you can't fix them, try to
-    # add comments here and/or in the file itself about
-    # why sweeping subject is tricky.
-    'zerver/lib/stream_topic.py',
-
     # This has lots of query data embedded, so it's hard
     # to fix everything until we migrate the DB to "topic".
     'zerver/tests/test_narrow.py',

zerver/lib/stream_topic.py

@@ -13,8 +13,8 @@ class StreamTopicTarget:
     '''
     This class is designed to help us move to a
     StreamTopic table or something similar.  It isolates
-    places where we are are still using `subject` or
-    `topic_name` as a key into tables.
+    places where we are are still using `topic_name` as
+    a key into tables.
     '''
     def __init__(self, stream_id: int, topic_name: str) -> None:
         self.stream_id = stream_id