[tools/perf] Remove RepeatableSynthesizeScrollGestureSharedState

It's dead code.

Bug: 921000
Change-Id: Id3987c57c14bfd642e7770927303508e92a272d6
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1602641
Auto-Submit: Juan Antonio Navarro Pérez <perezju@chromium.org>
Reviewed-by: Caleb Rouleau <crouleau@chromium.org>
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#658219}

tools/perf/page_sets/repeatable_synthesize_scroll_gesture_shared_state.py

-# Copyright 2015 The Chromium Authors. All rights reserved.
-# Use of this source code is governed by a BSD-style license that can be
-# found in the LICENSE file.
-import logging
-
-from telemetry.page import shared_page_state
-
-
-class RepeatableSynthesizeScrollGestureSharedState(
-    shared_page_state.SharedPageState):
-
-  def CanRunOnBrowser(self, browser_info, _):
-    if not browser_info.HasRepeatableSynthesizeScrollGesture():
-      logging.warning('Browser does not support repeatable scroll gestures, '
-                      'skipping test')
-      return False
-    return True