Remove now unnecessary -ms-viewport and -ms-overflow-style directives (#27789)

Edge/Mobile appears to have moved support for `-ms-viewport` behind a flag at some point, instead supporting meta viewport directives.
Removing this altogether also fixes issues in IE11 on high-dpi displays - see https://github.com/twbs/bootstrap/issues/21780

scss/bootstrap-grid.scss

@@ -5,10 +5,6 @@
  * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
  */
 
-@at-root {
-  @-ms-viewport { width: device-width; } // stylelint-disable-line at-rule-no-vendor-prefix
-}
-
 html {
   box-sizing: border-box;
   -ms-overflow-style: scrollbar;