refactor: change 'from' to upper case for a SQL command (#722)

* docs: lint fix for samples

* refactor: change 'from' to upper case for a SQL command

Author: vi3k6i5

django_spanner/introspection.py

@@ -355,7 +355,7 @@ def get_key_columns(self, cursor, table_name):
                 tc.COLUMN_NAME as column_name,
                 ccu.TABLE_NAME as referenced_table,
                 ccu.COLUMN_NAME as referenced_column
-            from
+            FROM
                 INFORMATION_SCHEMA.KEY_COLUMN_USAGE AS tc
             JOIN
                 INFORMATION_SCHEMA.REFERENTIAL_CONSTRAINTS as rc