docs(hooks): update image_save_progressive xrefs

Update 3 cross-references for image_save_progressive
from `class-wp-image-editor-imagick.php` to
`class-wp-image-editor-gd.php` where the filter's
PHPDoc block is located.

Related to https://core.trac.wordpress.org/ticket/64224

Author: apermo

src/wp-includes/rest-api/class-wp-rest-server.php

@@ -1388,11 +1388,11 @@ public function get_index( $request ) {
 			}
 			$available['image_output_formats'] = (object) $output_formats;
 
-			/** This filter is documented in wp-includes/class-wp-image-editor-imagick.php */
+			/** This filter is documented in wp-includes/class-wp-image-editor-gd.php */
 			$available['jpeg_interlaced'] = (bool) apply_filters( 'image_save_progressive', false, 'image/jpeg' );
-			/** This filter is documented in wp-includes/class-wp-image-editor-imagick.php */
+			/** This filter is documented in wp-includes/class-wp-image-editor-gd.php */
 			$available['png_interlaced'] = (bool) apply_filters( 'image_save_progressive', false, 'image/png' );
-			/** This filter is documented in wp-includes/class-wp-image-editor-imagick.php */
+			/** This filter is documented in wp-includes/class-wp-image-editor-gd.php */
 			$available['gif_interlaced'] = (bool) apply_filters( 'image_save_progressive', false, 'image/gif' );
 		}