Revert "[ios] Add testing config for StartSurface feature"

This reverts commit b69aa600f0492421595e05403b49975eda260069.

Reason for revert: speculative revert to fix NTPHomeTestCase on ios-simulator-noncq (see crbug.com/1213810), no other obvious suspects in blamelist while failure is consistent.

Original change's description:
> [ios] Add testing config for StartSurface feature
>
> StartSurface is then disabled for other test suites since
> an NTP may unexpectedly open.
>
> Change-Id: I4d7a538bfc93738c61e2fd76f0044f019883f0ac
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2911740
> Commit-Queue: Chris Lu <thegreenfrog@chromium.org>
> Reviewed-by: Gauthier Ambard <gambard@chromium.org>
> Reviewed-by: Javier Flores <javierrobles@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#886954}

Bug: 1213810
Change-Id: I961bb8c1a51a900f7ab1534529d6d90fdabe88bb
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2922111
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Owners-Override: Maksim Moskvitin <mmoskvitin@google.com>
Auto-Submit: Maksim Moskvitin <mmoskvitin@google.com>
Commit-Queue: Maksim Moskvitin <mmoskvitin@google.com>
Cr-Commit-Position: refs/heads/master@{#887126}