Revert "PreloadingDevTools: Disable prerendering for clients other than DevTools frontend"

This reverts commit 9d392f33.

Reason for revert: Suspect for making
http/tests/inspector-protocol/tracing/prerender.js  flaky on Mac:
https://ci.chromium.org/ui/p/chromium/builders/ci/Mac10.15%20Tests
https://ci.chromium.org/ui/p/chromium/builders/ci/Mac10.15%20Tests/39245/overview

Original change's description:
> PreloadingDevTools: Disable prerendering for clients other than DevTools frontend
>
> Prerendering introduced switching of FrameTreeNodes in the browser side
> and frame targets in the CDP client side. If a CDP client unaware of
> this logic and a prerendered page activated, it will cause unexpected
> behaviors. For example, Puppeteer loses control. To mitigate this, this
> CL disables prerendering if a target without tab target support is
> attached. For more details, see [1].
>
> [1] https://docs.google.com/document/d/12HVmFxYj5Jc-eJr5OmWsa2bqTJsbgGLKI6ZIyx0_wpA
>
> Bug: 1440085
> Change-Id: I80bf9234b60722112baf21c4fa2ee1f0d0cb3221
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4495911


> Reviewed-by: Danil Somsikov <dsv@chromium.org>
> Commit-Queue: Ken Okada <kenoss@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1158723}

Bug: 1440085, 1455943
Change-Id: I977f2a164081fdae5e7b54e4e8aa51088699280b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4624573


Owners-Override: Christoph Schwering <schwering@google.com>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Auto-Submit: Christoph Schwering <schwering@google.com>
Reviewed-by: Christoph Schwering <schwering@google.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1159585}