GitHub Actions: Improve readability of Pyre error output

[cclauss]

Pre-submission checklist

• [x] I've ran the linters locally and fixed lint errors related to the files I modified in this PR. You can install the linters by running pip install -r requirements-dev.txt && pre-commit install
• [x] pre-commit run

Summary

https://docs.python.org/3/library/json.html#module-json.tool will format sarif.json to improve readability.

Results in the failing test of:

• https://github.com/facebook/pyre-check/actions/runs/8823241730/job/24223253784

Test Plan

[facebook-github-bot]

@migeed-z has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.

[facebook-github-bot]

@migeed-z merged this pull request in facebook/pyre-check@c4912b6904be55d7d4312c7310bd3f7d5723a84f.