Fix typo in ai_*writer_test.cc

ai_writer_unittest.cc:
 - s/run_roop/run_loop/
 - s/mock_create_write_client/mock_create_writer_client/

ai_rewriter_unittest.cc:
 - s/run_roop/run_loop/
 - s/writer/rewriter/
 - s/mock_create_write_client/mock_create_rewriter_client/

Bug: 357967382, 358214322
Change-Id: I736b14baca7a45677a55692b4ad7cbfc98e5da56
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5796147


Reviewed-by: Mingyu Lei <leimy@chromium.org>
Commit-Queue: Tsuyoshi Horo <horo@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1343895}