Switch where variable output is being saved in check

[coatless]

Address the deprecation warning:

The set-output command is deprecated and will be disabled soon. Please upgrade to using Environment Files. For more information see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands

Pattern:

From:

- name: Set output
run: echo "::set-output name={name}::{value}"

To:

- name: Set output
run: echo "{name}={value}" >> $GITHUB_OUTPUT

More details:

https://docs.github.com/en/actions/using-workflows/workflow-commands-for-github-actions