Remove CSS definitions for some unused classes (#29279)

app/javascript/styles/mastodon-light/diff.scss

@@ -210,12 +210,6 @@ html {
   }
 }
 
-// Change the background colors of media and video spoilers
-.media-spoiler,
-.video-player__spoiler {
-  background: $ui-base-color;
-}
-
 .account-gallery__item a {
   background-color: $ui-base-color;
 }

app/javascript/styles/mastodon/components.scss

@@ -4325,35 +4325,6 @@ a.status-card {
   z-index: 100;
 }
 
-.media-spoiler {
-  background: $base-overlay-background;
-  color: $darker-text-color;
-  border: 0;
-  padding: 0;
-  width: 100%;
-  height: 100%;
-  border-radius: 4px;
-  appearance: none;
-
-  &:hover,
-  &:active,
-  &:focus {
-    padding: 0;
-    color: lighten($darker-text-color, 8%);
-  }
-}
-
-.media-spoiler__warning {
-  display: block;
-  font-size: 14px;
-}
-
-.media-spoiler__trigger {
-  display: block;
-  font-size: 11px;
-  font-weight: 700;
-}
-
 .spoiler-button {
   top: 0;
   inset-inline-start: 0;