Admin: Fix checked input state in older browsers.

Remove duplicate CSS setting the checked state for checkbox and radio inputs from `_admin.scss`. The duplicate selectors overrode the white checkmark in older browsers, impacting alternate color schemes.

Props sabernhardt, joedolson.
Fixes #64822.

git-svn-id: https://develop.svn.wordpress.org/trunk@61940 602fd350-edb4-49c9-b593-d223f7449a82

Author: joedolson

src/wp-admin/css/colors/_admin.scss

@@ -88,27 +88,12 @@ input[type="checkbox"]:checked {
 	border-color: var(--wp-admin-theme-color);
 }
 
-input[type=checkbox]:checked::before {
-	content: url("data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%27http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%27%20viewBox%3D%270%200%2020%2020%27%3E%3Cpath%20d%3D%27M14.83%204.89l1.34.94-5.81%208.38H9.02L5.78%209.67l1.34-1.25%202.57%202.4z%27%20fill%3D%27#{url-friendly-colour(variables.$form-checked)}%27%2F%3E%3C%2Fsvg%3E");
-	content: url("data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%27http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%27%20viewBox%3D%270%200%2020%2020%27%3E%3Cpath%20d%3D%27M14.83%204.89l1.34.94-5.81%208.38H9.02L5.78%209.67l1.34-1.25%202.57%202.4z%27%20fill%3D%27#{url-friendly-colour(variables.$form-checked)}%27%2F%3E%3C%2Fsvg%3E") / '';
-}
-
-// Checkbox checkmark - white for visibility on theme color background
-input[type="checkbox"]:checked::before {
-	content: url("data:image/svg+xml;utf8,%3Csvg%20xmlns%3D%27http%3A%2F%2Fwww.w3.org%2F2000%2Fsvg%27%20viewBox%3D%270%200%2020%2020%27%3E%3Cpath%20d%3D%27M14.83%204.89l1.34.94-5.81%208.38H9.02L5.78%209.67l1.34-1.25%202.57%202.4z%27%20fill%3D%27%23ffffff%27%2F%3E%3C%2Fsvg%3E") / '';
-}
-
 // Radio checked state - uses theme color
 input[type="radio"]:checked {
 	background: var(--wp-admin-theme-color);
 	border-color: var(--wp-admin-theme-color);
 }
 
-// Radio dot - white for visibility on theme color background
-input[type="radio"]:checked::before {
-	background: tokens.$white;
-}
-
 .wp-core-ui input[type="reset"]:hover,
 .wp-core-ui input[type="reset"]:active {
 	color: variables.$link-focus;