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This CL removes unused background tracing category presets so we
don't have to unnecessarily maintain them. This reduces technical
debt.

Bug: 1157487
Change-Id: I3d2c2eda3fa2ea730cf0cac46936733ea5f19862
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2586105
Commit-Queue: François Doray <fdoray@chromium.org>
Reviewed-by: ssid <ssid@chromium.org>
Cr-Commit-Position: refs/heads/master@{#841096}