parse_issues.yml workflow reporting deprecated use of set-output

This workflow https://github.com/adoptium/aqa-tests/blob/master/.github/workflows/parse-issues.yml (which is scheduled to run weekly, see https://github.com/adoptium/aqa-tests/actions/workflows/parse-issues.yml)

is now reporting this new 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/

As per the blog posted that is linked, this is newly deprecated as of Oct 11th. We should follow the instructions described in the post to fix the warning.

Start with .github/workflows/parse-issues.yml and the linked GitHub Actions deprecation guidance. Replace the deprecated output mechanism as described there, then run or inspect the weekly workflow to confirm the set-output warning no longer appears.

Written by the indexing model from the issue text.