Fix audio element width

src/shared/chat/styles/message-body.scss

@@ -8,18 +8,7 @@ converse-chat-message-body {
 
     audio {
         display: block;
-        @include media-breakpoint-down(sm) {
-            max-width: 95%;
-        }
-        @include media-breakpoint-up(md) {
-            max-width: 70%;
-        }
-        @include media-breakpoint-up(lg) {
-            max-width: 50%;
-        }
-        @include media-breakpoint-up(xl) {
-            max-width: 40%;
-        }
+        max-width: 95%;
     }
 
     video {