Remove default value for --size_format=<format>

Otherwise, it's included all of the time, which isn't expected.

Author: danielbachhuber

README.md

@@ -699,7 +699,6 @@ Available size formats include:
 	[--size_format=<format>]
 		Display the database size only, as a bare number.
 		---
-		default: b
 		options:
 		  - b
 		  - kb

src/DB_Command.php

@@ -680,7 +680,6 @@ public function tables( $args, $assoc_args ) {
 	 * [--size_format=<format>]
 	 * : Display the database size only, as a bare number.
 	 * ---
-	 * default: b
 	 * options:
 	 *   - b
 	 *   - kb