ref(PiP/actions): remove 'is ok to enter PiP' check

Currently enterPictureInPicture action can only be dispatched when
the app is on the conference view and the enter PiP button is displayed,
so no check should be necessary.

react/features/mobile/picture-in-picture/actions.js

         const state = getState();
         const { app } = state['features/app'];
 
-        // FIXME We want to be able to enter Picture-in-Picture as soon as we
-        // are on the Conference page i.e. even before `joining` was set in the
-        // reducer.
-        const { conference, joining } = state['features/base/conference'];
-
-        if (app
-                && app.props.pictureInPictureEnabled
-                && (conference || joining)) {
+        // XXX At the time of this writing this action can only be dispatched by
+        // the button which is on the conference view, which means that it's
+        // fine to enter PiP mode.
+        if (app && app.props.pictureInPictureEnabled) {
             const { PictureInPicture } = NativeModules;
             const p
                 = Platform.OS === 'android'