Twenty Twenty-One: Use esc_url() for the WordPress.org link in footer.php.

Props mukesh27, poena.
Merges [49762] into the 5.6 branch.
Fixes #51954.

git-svn-id: https://develop.svn.wordpress.org/branches/5.6@49853 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-content/themes/twentytwentyone/footer.php

@@ -58,7 +58,7 @@
 				printf(
 					/* translators: %s: WordPress. */
 					esc_html__( 'Proudly powered by %s.', 'twentytwentyone' ),
-					'<a href="' . esc_attr__( 'https://wordpress.org/', 'twentytwentyone' ) . '">WordPress</a>'
+					'<a href="' . esc_url( __( 'https://wordpress.org/', 'twentytwentyone' ) ) . '">WordPress</a>'
 				);
 				?>
 			</div><!-- .powered-by -->