chore: do not run e2e on PRs from forks

[alespour]

Proposed Changes

Changes CircleCI job not to run e2e tests on PRs from forks. CIRCLE_BRANCH env var is set to pull/NUMBER when run for fork PR: https://circleci.com/blog/triggering-trusted-ci-jobs-on-untrusted-forks/

Checklist

• [x] Tests pass
• [x] Commit messages are conventional

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 74.54%. Comparing base (61546e9) to head (d9b092e).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #77 +/- ## ========================================== - Coverage 83.09% 74.54% -8.56% ========================================== Files 12 12 Lines 994 994 ========================================== - Hits 826 741 -85 - Misses 138 228 +90 + Partials 30 25 -5 ```

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