Bug 1693969 - Remove default styling for :-moz-ui-{valid,invalid} pseudo-classes. r=xidorn

Other browsers don't have this UI, and there's no way to know whether
the form will actually be validated, so it can cause false-positives.

Depends on D105968

Differential Revision: https://phabricator.services.mozilla.com/D105969

layout/reftests/css-ui-invalid/default-style/style.css

@@ -1,13 +1,10 @@
 :not(output).invalid-ref {
-  box-shadow: 0 0 1.5px 1px red;
 }
 
 :not(output):-moz-focusring.invalid-ref {
-  box-shadow: 0 0 2px 2px rgba(255,0,0,0.4);
 }
 
 output.invalid-ref {
-  color: red;
 }
 
 .barred-ref {

layout/style/res/forms.css

@@ -721,22 +721,6 @@ optgroup:before {
   text-overflow: inherit;
 }
 
-/**
- * Set default style for invalid elements.
- */
-:-moz-ui-invalid {
-  box-shadow: 0 0 1.5px 1px red;
-}
-
-:-moz-ui-invalid:focus-visible {
-  box-shadow: 0 0 2px 2px rgba(255,0,0,0.4);
-}
-
-output:-moz-ui-invalid {
-  box-shadow: initial;
-  color: red;
-}
-
 @media print {
   input, textarea, select, button {
     -moz-user-input: none !important;