Replace deprecated command with environment file

[jongwooo]

Issue #, if available:

Resolve #505

Description of changes:

Update .github/workflows/integration.yml to use environment file instead of deprecated set-output command.
For more information, see: https://github.blog/changelog/2022-10-11-github-actions-deprecating-save-state-and-set-output-commands/

I found the workflow file that use set-output command through the following command:

$ find . -name '*.yml' -o -name '*.yaml' | xargs egrep '\bset-output\b'

AS-IS

run: echo "::set-output name=stack-name::$(echo graph-notebook-$RANDOM)"

TO-BE

run: echo "stack-name=$(echo graph-notebook-$RANDOM)" >> $GITHUB_OUTPUT

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[michaelnchin]

Nice catch, thank you @jongwooo !