[BUGFIX] Migrate deprecated set-output

GitHub deprecated `set-output` in favor of environment files due
to security reasons. See [1] for further information.

[1] https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

action.yml

@@ -113,4 +113,4 @@ runs:
       working-directory: t3docsproject
       run: |
         rm -Rf RenderedDocumentation
-        echo "::set-output name=renderedPath::t3docsproject/FinalDocumentation/"
+        echo "renderedPath=t3docsproject/FinalDocumentation/" >> $GITHUB_OUTPUT