Remove post-reaction verification refetch

Was doing an extra fetch_message per reaction to confirm the
reaction stuck. Turned out to be unrelated to the earlier
missing-reactions bug (that was the scan-state resume issue), so
drop it to save the API calls.

config.example.json

@@ -5,6 +5,5 @@
   "days_back": 10,
   "db_path": "reactions.sqlite3",
   "log_level": "INFO",
-  "manual_guild_ids": [],
-  "verify_reactions": true
+  "manual_guild_ids": []
 }