Remove Yahoo login support from core and deprecate OpenID2.0 (#7310)

- Plugin developers using OpenID2.0 should migrate to OAuth2 or OIDC. OpenID2.0 APIs will be removed in v2.4.0

- For sites requiring Yahoo login, it can be implemented using the OpenID Connect plugin: https://meta.discourse.org/t/103632

For more information, see https://meta.discourse.org/t/113249

app/assets/javascripts/admin/controllers/modals/admin-add-upload.js.es6

@@ -34,7 +34,6 @@ const SCSS_VARIABLE_NAMES = [
   "facebook",
   "cas",
   "twitter",
-  "yahoo",
   "github",
   "base-font-size",
   "base-line-height",