Fix hardcoded frame rate for frame by frame video navigation in web UI (#15198)

app/javascript/mastodon/features/ui/components/video_modal.js

@@ -64,6 +64,7 @@ export default class VideoModal extends ImmutablePureComponent {
         <div className='video-modal__container'>
           <Video
             preview={media.get('preview_url')}
+            frameRate={media.getIn(['meta', 'original', 'frame_rate'])}
             blurhash={media.get('blurhash')}
             src={media.get('url')}
             currentTime={options.startTime}