Update wishlist_email_rss.xml

This is reproduced on Feestwinken and Grasscity so for sure on M2:2.1.9

Firstly, login to your admin area and navigate to Stores> Configuration. Then click to expand Catalog tab and select RSS Feeds. Then enable ths RSS feeds for Wishlist. After that follow the steps:

1. Open the front-end of a magneto 2 installation.
2. Login
3. Add multiple product to wish list
4. Go to My Account> My wish list
5. Ckeck on "Share wish list"
6. Choose to use RSS feed in Checkbox and submit Share Wish List