Bug 1877512 - change feature-callout dismiss-button background color to transparent r=aminomancer,omc-reviewers

Differential Revision: https://phabricator.services.mozilla.com/D209302

browser/components/aboutwelcome/content/aboutwelcome.css

@@ -434,7 +434,7 @@ div#feature-callout.hidden {
   inset-inline: auto 0;
   margin-block: 16px 0;
   margin-inline: 0 16px;
-  background-color: var(--fc-background);
+  background-color: transparent;
 }
 #feature-callout .screen[pos=callout] .section-main .dismiss-button[button-size=small] {
   height: 24px;

browser/components/asrouter/content-src/styles/_feature-callout.scss

@@ -359,7 +359,7 @@
           inset-inline: auto 0;
           margin-block: 16px 0;
           margin-inline: 0 16px;
-          background-color: var(--fc-background);
+          background-color: transparent;
 
           &[button-size='small'] {
             height: 24px;