Update E2E testing section in README
Background
The recent changes to e2e test setup haven't been documented in README:
What to change
- Design: n/a
- Research: n/a
- Spec: n/a
- Legal: n/a
- Development: update end-to-end testing section in the README: https://gitlab.com/adblockinc/ext/adblockplus/adblockplus#end-to-end-testing with the latest instructions on how to run E2E tests locally and in lambdatest
Hints for testers
n/a
Hints for translators
n/a