Use Node V20 in Github CI (#167)

Summary:
The CI job has been failing. Use the same version as what the relay repo is using https://github.com/facebook/relay/blob/main/.github/workflows/ci.yml

Pull Request resolved: #167

Reviewed By: evanyeung

Differential Revision: D67885317

Pulled By: tyao1

fbshipit-source-id: 81ce4740ed7a30606c8cd3ebc62cdd15343cf5a2

Author: tyao1

.github/workflows/ci.yml

@@ -15,7 +15,7 @@ jobs:
       - uses: actions/checkout@v1
       - uses: actions/setup-node@v1
         with:
-          node-version: 12.x
+          node-version: 20.x
       - name: Install dependencies
         run: yarn install --frozen-lockfile
       - name: Check formatting