[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/features/compose/components/dropdown_menu.jsx

@@ -169,7 +169,7 @@ export default class ComposerOptionsDropdownContent extends React.PureComponent
         onClick={this.handleClick}
         onKeyDown={this.handleKeyDown}
         role='option'
-        tabIndex='0'
+        tabIndex={0}
         key={name}
         data-index={i}
         ref={active ? this.setFocusRef : null}