[iOS] Fixing GoogleServicesSettingsTestCase

grey_swipeSlowInDirection() was scrolling too far, and according to the
size of the scrollview, cell was moved out of the screen without being
seen.
It is now replaced with grey_scrollInDirection()
Issue introduced with crrev.com/c/1158404

TBR: sczs
Cq-Include-Trybots: luci.chromium.try:ios-simulator-full-configs;master.tryserver.chromium.mac:ios-simulator-cronet
Change-Id: I1d4c198b035ed0ddc0acf58af9638c61bb2d9ab2
Reviewed-on: https://chromium-review.googlesource.com/1166902Reviewed-by: Jérôme Lebel <jlebel@chromium.org>
Commit-Queue: Jérôme Lebel <jlebel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#581506}

ios/chrome/browser/ui/settings/google_services_settings_egtest.mm

@@ -175,7 +175,7 @@ using unified_consent::prefs::kUnifiedConsentGiven;
                                    grey_kindOfClass(
                                        [UICollectionViewCell class]),
                                    grey_sufficientlyVisible(), nil)]
-         usingSearchAction:grey_swipeSlowInDirection(kGREYDirectionUp)
+         usingSearchAction:grey_scrollInDirection(kGREYDirectionDown, 150)
       onElementWithMatcher:self.scrollViewMatcher]
       assertWithMatcher:grey_notNil()];
 }