Update error string in test assertion to match upstream 10.0.2

Signed-off-by: Andrew Mason <amason@slack-corp.com>

go/vt/vtgate/executor_select_test.go

@@ -2323,7 +2323,7 @@ func TestSelectFromInformationSchema(t *testing.T) {
  // check failure when trying to query two keyspaces
  _, err := exec(executor, session, "SELECT B.TABLE_NAME FROM INFORMATION_SCHEMA.TABLES AS A, INFORMATION_SCHEMA.COLUMNS AS B WHERE A.TABLE_SCHEMA = 'TestExecutor' AND A.TABLE_SCHEMA = 'TestXBadSharding'")
  require.Error(t, err)
- require.Contains(t, err.Error(), "specifying two different database in the query is not supported")
+ require.Contains(t, err.Error(), "two predicates for specifying the database are not supported")
 
  // we pick a keyspace and query for table_schema = database(). should be routed to the picked keyspace
  session.TargetString = "TestExecutor"