Revert "Remove limitation on "wp db size" (#5507)" (#5522)

This reverts commit 2efcab4.

Revert "Remove limitation on "wp db size" (#5507)"

This reverts commit 720c8b9.

Author: rebeccahum

lib/helpers/wp-cli-db/class-wp-cli-db.php

@@ -49,6 +49,7 @@ public function validate_subcommand( array $command ) {
 			'query',
 			'prefix',
 			'columns',
+			'size',
 			'tables',
 		];