remove user survery banner (#145)

Author: andersy005

_config.yml

@@ -8,7 +8,6 @@ only_build_toc_files: true
 # See https://jupyterbook.org/customize/config.html#add-a-link-to-your-repository
 html:
   # NOTE: this announcement shows up on all pages
-  announcement: 'ℹ️ The 2022 Xarray User Survey is out! Please take ~5 minutes to help improve Xarray! <a href="https://docs.google.com/forms/d/e/1FAIpQLSfnMd8UsC1XP1lPuFczl148VfpmwnFu4a0Z94odt1L6U0R0Pw/viewform">LINK</a>'
   home_page_in_navbar: false
   use_edit_page_button: true
   use_issues_button: true