Don't show composer send button if user cannot send (#11298)

Such as when room is tombstoned

Author: t3chguy

src/components/views/rooms/MessageComposer.tsx

@@ -588,7 +588,7 @@ export class MessageComposer extends React.Component<IProps, IState> {
             />,
         );
 
-        const showSendButton = !this.state.isComposerEmpty || this.state.haveRecording;
+        const showSendButton = canSendMessages && (!this.state.isComposerEmpty || this.state.haveRecording);
 
         const classes = classNames({
             "mx_MessageComposer": true,