fix(maintenance): drop a duplicated comment block above the database guard

The four-line comment explaining why an empty database must be rejected
was pasted twice above the guard in create_maintenance_job(). Comment
only; no behaviour change.

web/pgadmin/tools/maintenance/__init__.py

@@ -217,10 +217,6 @@ def create_maintenance_job(sid, did):
     if validation_error is not None:
         return bad_request(errormsg=validation_error)
 
-    # A target database is mandatory. Reject an empty/missing value up front:
-    # otherwise PGDATABASE is left unset and libpq falls back down its chain to
-    # a database named after the login role, silently running maintenance on
-    # the wrong database instead of failing safely.
     # A target database is mandatory. Reject an empty/missing value up front:
     # otherwise PGDATABASE is left unset and libpq falls back down its chain to
     # a database named after the login role, silently running maintenance on