ci: Use GITHUB_OUTPUT envvar instead of set-output command

`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

Signed-off-by: Arun <[email protected]>

.github/workflows/iso-ci.yaml

@@ -58,7 +58,7 @@ jobs:
 
     - name: set output
       id: vars
-      run: echo "::set-output name=sha_short::$(git rev-parse --short HEAD)"
+      run: echo "sha_short=$(git rev-parse --short HEAD)" >> "$GITHUB_OUTPUT"
 
     - name: get tag without v
       id: tag