Give video player fluid max-width (#4935)

app/javascript/styles/components.scss

@@ -3810,6 +3810,7 @@ button.icon-button.active i.fa-retweet {
   overflow: hidden;
   position: relative;
   background: $base-shadow-color;
+  max-width: 100%;
 
   video {
     height: 100%;