Revert "Update add_issue_to_project.yml" (#4841)

Reverts #4839

Need to use a PAT for this workflow because as of 1/2024 the
GITHUB_TOKEN can not be given write access to a project board.

Refer to [possible permissions
here](https://docs.github.com/en/actions/security-guides/automatic-token-authentication#permissions-for-the-github_token)
for more information.

.github/workflows/add_issue_to_project.yml

@@ -12,4 +12,4 @@ jobs:
       - uses: actions/[email protected]
         with:
           project-url: https://github.com/orgs/dbt-labs/projects/14 
-          github-token: ${{ secrets.GITHUB_TOKEN }}
+          github-token: ${{ secrets.DOCS_SECRET }}