startup benchmarks cleanup: remove 'pageset_repeat': 1'

This code doesn't do anything:

The pageset_repeat option is used to set the default for the flag
'--pageset-repeat'. The default is 1. If someone passes in
--pageset-repeat=3 over the commandline then that will override
this option either way.

See https://goo.gl/JZ2yZQ. I am attempting to redesign this
system a bit, and I noticed this code.

Bug: 894254
Change-Id: I80da537180384f8b4b4ed25c87f9c9c8f814b2d5
Reviewed-on: https://chromium-review.googlesource.com/c/1356131Reviewed-by: Ned Nguyen <nednguyen@google.com>
Commit-Queue: Ned Nguyen <nednguyen@google.com>
Cr-Commit-Position: refs/heads/master@{#612525}

tools/perf/benchmarks/startup_mobile.py

@@ -212,10 +212,6 @@ class _MobileStartupStorySet(story_module.StorySet):
 class MobileStartupBenchmark(perf_benchmark.PerfBenchmark):
   SUPPORTED_PLATFORMS = [story_module.expectations.ANDROID_NOT_WEBVIEW]
 
-  # Set |pageset_repeat| to 1 to control the amount of iterations from the
-  # stories. This would avoid setting per-story pageset_repeat at bisect time.
-  options = {'pageset_repeat': 1}
-
   def CreateCoreTimelineBasedMeasurementOptions(self):
     cat_filter = chrome_trace_category_filter.ChromeTraceCategoryFilter(
         filter_string=('navigation,loading,net,netlog,network,offline_pages,'