Update github-script action REST calls

Breaking changed introduced in actions/github-script@v6.
https://github.com/actions/github-script#breaking-changes-in-v5

.github/workflows/nightly-release.yml

@@ -43,7 +43,7 @@ jobs:
           github-token: ${{ secrets.GITHUB_TOKEN }}
           script: |
             try {
-                await github.git.deleteRef({
+                await github.rest.git.deleteRef({
                   owner: context.repo.owner,
                   repo: context.repo.repo,
                   ref: "tags/nightly"
@@ -51,7 +51,7 @@ jobs:
             } catch (e) {
               console.log("Warning: The nightly tag doesn't exist yet, so there's nothing to do. Trace: " + e)
             }
-            await github.git.createRef({
+            await github.rest.git.createRef({
               owner: context.repo.owner,
               repo: context.repo.repo,
               ref: "refs/tags/nightly",