Remove usage of prefs::kDataSaverEnabled in DataSaverBrowserTest

One of several CLs to clean up usage of this pref.

Bug: 934399
Change-Id: I1f7bde328ca2d9b99b0e573afedc2589cc3fc0dd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1529755
Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642635}
3 files changed