Hide registered and users columns in Sites table on small screens to prevent columms from becoming too narrow. Fixes #25973, props johnbillion.

git-svn-id: https://develop.svn.wordpress.org/trunk@26416 602fd350-edb4-49c9-b593-d223f7449a82

src/wp-admin/css/wp-admin.css

@@ -11602,6 +11602,15 @@ li#wp-admin-bar-menu-toggle {
 		width: 30%;
 	}
 
+	/* Network admin sites */
+	.sites .column-registered, .sites .column-users {
+		display: none;
+	}
+
+	.sites .column-blogname {
+		width: 55%;
+	}
+
 	/* Updates */
 	#wpbody-content #update-themes-table .plugin-title {
 		width: auto;