docs(test): correct the feed-views fixture comment on topic tag distribution

chA/chB each carry a different topic tag (T1 vs T2), not both — the old comment
implied they shared T1/T2. Assertions unchanged (equivalence test).

backend/tests/test_feed_views.py

@@ -108,7 +108,8 @@ def _seed_tagged(db, make_user):
     # channel -> (system) tag keys. chA carries two languages (L1+L2); chC two "other" tags (O1+O2)
     # AND chA carries O1 too — so the per-category any/all match narrows NON-TRIVIALLY (AND != OR) for
     # language and other, not only topic: e.g. other {O1,O2} → OR {chA,chC} vs AND {chC}; language
-    # {L1,L2} → OR {chA,chB,chC} vs AND {chA}. (chA/chB share topic tags T1/T2 for the topic case.)
+    # {L1,L2} → OR {chA,chB,chC} vs AND {chA}. (For topic, chA and chB each carry a DIFFERENT topic tag
+    # — T1 vs T2 — so topic {T1,T2} → OR {chA,chB,chC} vs AND {} empty.)
     links = {
         "chA": ["L1", "L2", "T1", "O1"],
         "chB": ["L1", "T2"],