Fix remove db from connection string (CTFd#2372)

Fix ping.py calling .set instead of ._replace

Author: senacor-swr

ping.py

@@ -17,7 +17,7 @@
 
 # Null out the database so raw_connection doesnt error if it doesnt exist
 # CTFd will create the database if it doesnt exist
-url = url.set(database=None)
+url = url._replace(database=None)
 
 # Wait for the database server to be available
 engine = create_engine(url)