docs(cli): clarify what pause-at does

[Lazizbek Ergashev (lazerg)]

Summary

• The Test Debugging page annotated playwright-cli pause-at test.ts:42 as "set a breakpoint", but the command does not just arm a breakpoint: it resumes the paused test and runs it up to that location before pausing again (browser_resume with a location calls debugger.runTo).
• Reworded the comment to match, in line with the command's own description ("Run the test up to a specific location and pause there").

Fixes microsoft/playwright#42389