AWS Lambda test suite doesn't work on contributor PRs

[sentrivana]

Problem Statement

The AWS Lambda test suite fails on all PRs created from forks -- so all contributor PRs.

Solution Brainstorm

Look at how the Trigger: getsentry tests label is set up in the sentry repo and see if we can reuse the behavior.

• https://securitylab.github.com/research/github-actions-preventing-pwn-requests/
• https://nathandavison.com/blog/github-actions-and-the-threat-of-malicious-pull-requests