Typo in drop SQLite database

(transplanted from 40b287b932535d23c7bc837eaeff78a35e06f81d)

trytond/backend/sqlite/database.py

@@ -150,7 +150,7 @@ class Database(DatabaseInterface):
         conn.close()
 
     def drop(self, cursor, database_name):
-        if database_name == ':memory':
+        if database_name == ':memory:':
             self._conn = None
             return
         if os.sep in database_name: