chore: fix issue template discord link (#21885)

<!--
Before submitting a PR, please read https://deno.com/manual/contributing

1. Give the PR a descriptive title.

  Examples of good title:
    - fix(std/http): Fix race condition in server
    - docs(console): Update docstrings
    - feat(doc): Handle nested reexports

  Examples of bad title:
    - fix #7123
    - update docs
    - fix bugs

2. Ensure there is a related issue and it is referenced in the PR text.
3. Ensure there are tests that cover the changes.
4. Ensure `cargo test` passes.
5. Ensure `./tools/format.js` passes without changing files.
6. Ensure `./tools/lint.js` passes.
7. Open as a draft PR if your work is still in progress. The CI won't
run
   all steps, but you can add '[ci]' to a commit message to force it to.
8. If you would like to run the benchmarks on the CI, add the 'ci-bench'
label.
-->
Fixes https://github.com/denoland/deno/issues/21880

.github/ISSUE_TEMPLATE/config.yml

@@ -4,5 +4,5 @@ contact_links:
     url: https://github.com/denoland/deploy_feedback/
     about: Provide feature requests or bug reports for the Deno Deploy edge runtime.
   - name: 💬 Discord
-    url: https://discord.com/deno
+    url: https://discord.gg/deno
     about: Join our community on Discord.