Revert "docs(gh): replace gitter with discussion link"

This reverts commit a296fcfed4.

.github/ISSUE_TEMPLATE/config.yml

@@ -1,5 +1,5 @@
 blank_issues_enabled: false
 contact_links:
   - name: Question
-    url: https://github.com/nvim-telescope/telescope.nvim/discussions
-    about: Ask about configuration and usage of Telescope
+    url: https://github.com/neovim/neovim/discussions
+    about: Ask about configuration and usage of Nvim