[Glitch] Ensure tabIndex is number instead of string

Port ec0c104bf2 to glitch-soc

Signed-off-by: Claire <claire.github-309c@sitedethib.com>

app/javascript/flavours/glitch/components/picture_in_picture_placeholder.jsx

@@ -58,7 +58,7 @@ class PictureInPicturePlaceholder extends React.PureComponent {
     const { height } = this.state;
 
     return (
-      <div ref={this.setRef} className='picture-in-picture-placeholder' style={{ height }} role='button' tabIndex='0' onClick={this.handleClick}>
+      <div ref={this.setRef} className='picture-in-picture-placeholder' style={{ height }} role='button' tabIndex={0} onClick={this.handleClick}>
         <Icon id='window-restore' />
         <FormattedMessage id='picture_in_picture.restore' defaultMessage='Put it back' />
       </div>