Remove mention of BattOrs from perf trybot docs

TBR=nednguyen@chromium.org

Bug: 859514
Change-Id: I5aa3aa1ca04eb69ddf3d9d28713df353f4f68b10
Reviewed-on: https://chromium-review.googlesource.com/1169440
Commit-Queue: Charlie Andrews <charliea@chromium.org>
Reviewed-by: Charlie Andrews <charliea@chromium.org>
Cr-Commit-Position: refs/heads/master@{#582164}

docs/speed/perf_trybots.md

@@ -14,7 +14,6 @@ patch applied.
   continuous integration suite.
 * The devices have the "maintenance mutex" enabled, reducing noise from
   background processes.
-* The devices are instrumented with BattOrs for power measurements.
 * Some regressions take multiple repeats to reproduce, and Pinpoint
   automatically runs multiple times and aggregates the results.
 * Some regressions reproduce on some devices but not others, and Pinpoint will