fix(sqlite): Use DEFERRED isolation level

sqlite connection starts with no transaction if isolation level hasn't provided

frappe/database/sqlite/database.py

@@ -105,7 +105,6 @@ class SQLiteDatabase(SQLiteExceptionUtil, Database):
 
 	def get_connection(self, read_only: bool = False):
 		conn = self.create_connection(read_only)
-		conn.isolation_level = None
 		conn.create_function("regexp", 2, regexp)
 		conn.create_function("regexp_replace", 3, regexp_replace)
 		pragmas = {