Cache API: Remove unused usermeta global cache group.

The `usermeta` group was introduced in WP 2.0, but was never actually used in WordPress core.

The `user_meta` group is used instead.

Follow-up to [3011], [15482], [16562], [53823], [53832], [54940].

Props ignatggeorgiev, peterwilsoncc, oglekler, pamprn09, spacedmonkey, SergeyBiryukov.
Fixes #58175.

git-svn-id: https://develop.svn.wordpress.org/trunk@55940 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-includes/load.php

@@ -772,10 +772,9 @@ function wp_start_object_cache() {
 				'rss',
 				'users',
 				'user-queries',
+				'user_meta',
 				'useremail',
 				'userlogins',
-				'usermeta',
-				'user_meta',
 				'userslugs',
 			)
 		);

src/wp-includes/ms-blogs.php

@@ -569,10 +569,9 @@ function switch_to_blog( $new_blog_id, $deprecated = null ) {
 						'rss',
 						'users',
 						'user-queries',
+						'user_meta',
 						'useremail',
 						'userlogins',
-						'usermeta',
-						'user_meta',
 						'userslugs',
 					)
 				);
@@ -663,10 +662,9 @@ function restore_current_blog() {
 						'rss',
 						'users',
 						'user-queries',
+						'user_meta',
 						'useremail',
 						'userlogins',
-						'usermeta',
-						'user_meta',
 						'userslugs',
 					)
 				);

tests/phpunit/includes/abstract-testcase.php

@@ -413,10 +413,9 @@ abstract class WP_UnitTestCase_Base extends PHPUnit_Adapter_TestCase {
 				'rss',
 				'users',
 				'user-queries',
+				'user_meta',
 				'useremail',
 				'userlogins',
-				'usermeta',
-				'user_meta',
 				'userslugs',
 			)
 		);