ci: Use GITHUB_OUTPUT envvar instead of set-output command (#1193)

Summary:
`save-state` and `set-output` commands used in GitHub Actions are deprecated and [GitHub recommends using environment files](https://github.blog/changelog/2023-07-24-github-actions-update-on-save-state-and-set-output-commands/).

This PR updates the usage of `set-output` to `$GITHUB_OUTPUT`

Instructions for envvar usage from GitHub docs:

https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions#setting-an-output-parameter

Pull Request resolved: #1193

Reviewed By: NickGerleman

Differential Revision: D52891159

Pulled By: robhogan

fbshipit-source-id: 1d837c76675ee786c638eb538154da9fcb949e5f

.github/workflows/deploy-website.yml

@@ -35,7 +35,7 @@ jobs:
 
       - name: Get yarn cache directory
         id: yarn
-        run: echo "::set-output name=dir::$(yarn cache dir)"
+        run: echo "dir=$(yarn cache dir)" >> $GITHUB_OUTPUT
 
       - name: Restore yarn cache
         uses: actions/cache@v3.3.2