Documentation for adding example command for running E2E specs locally

What does this MR do and why?

Adds an example command in QA documentation for running an E2E spec locally against GDK with bundle exec rspec.

Relates to: gitlab-org/quality/quality-engineering/team-tasks#1905 (closed)

Screenshots or screen recordings

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Before	After

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

MR acceptance checklist

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