Fix media modal buttons not showing up on mobile (#15417)

Fixes #15374

When the pop-out player was introduced, it had tweaks for the mobile
view, but it's now disabled in mobile mode and the styling was reused
for modals, causing the footer to be hidden on mobile without a good
reason.

Co-authored-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/styles/mastodon/components.scss

@@ -7194,21 +7194,6 @@ noscript {
   .audio-player {
     border-radius: 0;
   }
-
-  @media screen and (max-width: 415px) {
-    width: 210px;
-    bottom: 10px;
-    right: 10px;
-
-    &__footer {
-      display: none;
-    }
-
-    .video-player,
-    .audio-player {
-      border-radius: 0 0 4px 4px;
-    }
-  }
 }
 
 .picture-in-picture-placeholder {