Coding Standards: Remove unnecessary isset() check in Custom_Image_Header::step_2().

The only path where `$oitar` is not set returns in an earlier conditional.

Follow-up to [20806].

Props justlevine.
See #63268.

git-svn-id: https://develop.svn.wordpress.org/trunk@60351 602fd350-edb4-49c9-b593-d223f7449a82

Author: SergeyBiryukov

src/wp-admin/includes/class-custom-image-header.php

@@ -951,7 +951,7 @@ public function step_2() {
 	<p class="submit">
 		<?php submit_button( __( 'Crop and Publish' ), 'primary', 'submit', false ); ?>
 		<?php
-		if ( isset( $oitar ) && 1 === $oitar
+		if ( 1 === $oitar
 			&& ( current_theme_supports( 'custom-header', 'flex-height' )
 				|| current_theme_supports( 'custom-header', 'flex-width' ) )
 		) {