Build/Test Tools: Update PHPCompatibilityWP to version 2.1.3.

The latest release takes the new polyfills added in WordPress 5.9 into account.

This commit also removes redundant inline ignore comments for WP-polyfilled functionality. The PHPCompatibilityWP ruleset explicitly excludes those polyfills, so they don't need to be annotated as ignored.

Release notes:
https://github.com/PHPCompatibility/PHPCompatibilityWP/releases/tag/2.1.3

For a full list of changes in this update, see the PHPCompatibilityWP GitHub:
https://github.com/PHPCompatibility/PHPCompatibilityWP/compare/2.1.2...2.1.3

Follow-up to [46290], [51543].

Props jrf.
Fixes #54711.

git-svn-id: https://develop.svn.wordpress.org/trunk@52425 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/media.php

@@ -5196,7 +5196,7 @@ function wp_getimagesize( $filename, array &$image_info = null ) {
 			return array(
 				$width,
 				$height,
-				IMAGETYPE_WEBP, // phpcs:ignore PHPCompatibility.Constants.NewConstants.imagetype_webpFound
+				IMAGETYPE_WEBP,
 				sprintf(
 					'width="%d" height="%d"',
 					$width,