Update database type for Showdown contests in app.py

- Changed the database type identifier for Showdown contests from 'sd' to 'showdown' to improve clarity and consistency in the codebase.

app.py

@@ -61,7 +61,7 @@ def grab_contest_payout_info(db, sport, type, contest_date, contest_name, contes
     if type == 'Classic':
         db_type = 'reg'
     elif type == 'Showdown':
-        db_type = 'sd'
+        db_type = 'showdown'
     collection = db[f'{sport}_{db_type}_payout_info']
     cursor = collection.find()