Adjusting .sr mixins for NVDA/JAWS on Windows

common/static/sass/_mixins.scss

@@ -404,14 +404,10 @@
 // +Content - Screenreader Text - Extend
 // ====================
 %cont-text-sr {
-  border: 0;
-  clip: rect(0 0 0 0);
-  height: 1px;
-  margin: -1px;
-  overflow: hidden;
-  padding: 0;
+  // clip has been deprecated but is still supported
+  clip: rect(1px 1px 1px 1px);
+  clip: rect(1px, 1px, 1px, 1px);
   position: absolute;
-  width: 1px;
 }
 
 // +Content - Text Wrap - Extend

lms/static/sass/base/_mixins.scss

@@ -125,14 +125,10 @@
 
 // extends -hidden elems - screenreaders
 %text-sr {
-  border: 0;
+  // clip has been deprecated but is still supported
   clip: rect(1px 1px 1px 1px);
-  height: 1px;
-  margin: -1px;
-  overflow: hidden;
-  padding: 0;
+  clip: rect(1px, 1px, 1px, 1px);
   position: absolute;
-  width: 1px;
 }
 
 // extends - ensures proper contrast for automated checkers