[Glitch] Fix “Alt text” button submitting form in moderation interface

Port 973eb0a1d3 to glitch-soc

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

app/javascript/flavours/glitch/components/alt_text_badge.tsx

@@ -28,6 +28,7 @@ export const AltTextBadge: React.FC<{
   return (
     <>
       <button
+        type='button'
         ref={anchorRef}
         className='media-gallery__alt__label'
         onClick={handleClick}