[WORKFLOW] issues & pr templates (squash) fix link to CONTRIBUTING.md

Reviewed-on: https://codeberg.org/forgejo/forgejo/pulls/2232

Co-authored-by: oliverpool <[email protected]>
Co-committed-by: oliverpool <[email protected]>
(cherry picked from commit 8c0e5d07f8a95ebe4e6102591302effbe13f58e3)
(cherry picked from commit 77716e7cd4c2e5ecfab5fcf1a5d8d2b3b3f778aa)
(cherry picked from commit d0d004fe027e2af6e2ef8487b9d04c4f5b42352f)

Author: oliverpool

.gitea/pull_request_template.md

@@ -1,4 +1,4 @@
 <!--
 Before submitting a PR, please read the contributing guidelines:
-https://codeberg.org/forgejo/forgejo/src/branch/main/CONTRIBUTING.md
+https://codeberg.org/forgejo/forgejo/src/branch/forgejo/CONTRIBUTING.md
 -->