Remove unreadable alt attribute from the room status bar warning icon (nonsense to screenreaders) (#10402)

And the other content like the title already describe what's going on sufficiently.

Split out from https://github.com/matrix-org/matrix-react-sdk/pull/8354

src/components/structures/RoomStatusBar.tsx

@@ -282,8 +282,7 @@ export default class RoomStatusBar extends React.PureComponent<IProps, IState> {
                                 src={require("../../../res/img/feather-customised/warning-triangle.svg").default}
                                 width="24"
                                 height="24"
-                                title="/!\ "
-                                alt="/!\ "
+                                alt=""
                             />
                             <div>
                                 <div className="mx_RoomStatusBar_connectionLostBar_title">