General: Use correct value for the speak property in various CSS files.

Follow-up to [49263].

Props hareesh-pillai.
Fixes #51622.
Built from https://develop.svn.wordpress.org/trunk@49309


git-svn-id: http://core.svn.wordpress.org/trunk@49071 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/css/media.css

@@ -321,7 +321,7 @@
 #find-posts-close:before {
 	font: normal 20px/36px dashicons;
 	vertical-align: top;
-	speak: none;
+	speak: never;
 	-webkit-font-smoothing: antialiased;
 	-moz-osx-font-smoothing: grayscale;
 	content: "\f158";
@@ -958,7 +958,7 @@ border color while dragging a file over the uploader drop area */
 .imgedit-menu .button:before {
 	font: normal 16px/1 dashicons;
 	margin-right: 8px;
-	speak: none;
+	speak: never;
 	vertical-align: middle;
 	position: relative;
 	top: -2px;