[PLT-7051] Fix hide/show for CMD/CTRL + Shift + A keyboard shortcut (#6979)

* fix hide/show for CMD/CTRL + Shift + A keyboard shortcut

* simplify setting value of show

webapp/components/user_settings/user_settings_modal.jsx

@@ -114,7 +114,7 @@ class UserSettingsModal extends React.Component {
     handleKeyDown(e) {
         if (Utils.cmdOrCtrlPressed(e) && e.shiftKey && e.keyCode === Constants.KeyCodes.A) {
             this.setState({
-                show: true
+                show: !this.state.show
             });
         }
     }