fix typo

Change-Id: I887507fa33ea30f5859707063326934e5c11208f

Author: Jon Wayne Parrott

samples/samples/snippets.py

@@ -378,7 +378,7 @@ def read_only_transaction(instance_id, database_id):
     instance = spanner_client.instance(instance_id)
     database = instance.database(database_id)
 
-    with database.snapshot(mutli_use=True) as snapshot:
+    with database.snapshot(multi_use=True) as snapshot:
         # Read using SQL.
         results = snapshot.execute_sql(
             'SELECT SingerId, AlbumId, AlbumTitle FROM Albums')