[benchmarking] Remove timing data which is no longer in use

Some of the timing data files under src/tools/perf/core/shard_maps/timing_data
are no longer in use. This CL will simply removed those files.

For those being removed, I've verified that no corresponding _map.json files
exists.

Bug: chromium:1013767
Change-Id: Iedbc01884d4e115d63ad8b044e8d7100716ce199
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1857643Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: Wenbin Zhang <wenbinzhang@google.com>
Cr-Commit-Position: refs/heads/master@{#705729}

tools/perf/core/shard_maps/timing_data/pixel2_webview_story_timing.json

-[]
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