remove uses of -moz-proton media query

chrome/combined_favicon_and_tab_close_button.css

@@ -7,7 +7,8 @@ See the above repository for updates as well as full license text. */
   -moz-box-ordinal-group: 0;
   display: -moz-box !important;
   position: relative;
-  margin-inline: -1px -19px !important;
+  margin-inline: -4px -20px !important;
+  padding-inline-start: 7px !important;
   z-index: -1;
   visibility: hidden;
   width: unset !important;
@@ -18,13 +19,6 @@ See the above repository for updates as well as full license text. */
   background-image: linear-gradient(var(--toolbarbutton-hover-background),var(--toolbarbutton-hover-background))
 }
 
-@media (-moz-proton){
-  .tab-close-button{
-    margin-inline: -4px -20px !important;
-    padding-inline-start: 7px !important;
-  }
-}
-
 /**** ONLY USE ONE OF THE FOLLOWING ****/
 /**** These select the behavior of a scenario where the page has no favicon ****/