Revert "Adding DumpWithoutCrashing if StartLoad happens in an MHTML."

This reverts commit bbc4b0fe.

Reason for revert: Gathered sufficient diagnostics - DwoC reports can be found in https://crbug.com/1164906

Original change's description:
> Adding DumpWithoutCrashing if StartLoad happens in an MHTML.
>
> MHTML documents should never trigger HTML requests.  Let's double-check
> this with an explicit DumpWithoutCrashing added in this CL.
>
> Bug: 1151438
> Change-Id: I7a518308d85d58cb15deeec579df2f1c41e6abb6
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2597028
> Commit-Queue: Yutaka Hirano <yhirano@chromium.org>
> Auto-Submit: Łukasz Anforowicz <lukasza@chromium.org>
> Reviewed-by: Yutaka Hirano <yhirano@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#838787}

TBR=yhirano@chromium.org,lukasza@chromium.org,chromium-scoped@luci-project-accounts.iam.gserviceaccount.com

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1151438
Change-Id: I202fc1fdc6972ae6b028d4e89b4d827663d3e06d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2624532Reviewed-by: Łukasz Anforowicz <lukasza@chromium.org>
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Cr-Commit-Position: refs/heads/master@{#842656}

third_party/blink/renderer/platform/loader/fetch/resource_fetcher.cc

@@ -1985,15 +1985,6 @@ bool ResourceFetcher::StartLoad(Resource* resource,
 
   ResourceLoader* loader = nullptr;
 
-  if (archive_ && resource->Url().ProtocolIsInHTTPFamily()) {
-    // MHTML documents should not trigger HTTP requests.
-    //
-    // TODO(lukasza): https://crbug.com/1151438: Remove the ad-hoc debugging
-    // below, once the bug is understood.
-    NOTREACHED();
-    base::debug::DumpWithoutCrashing();
-  }
-
   {
     // Forbids JavaScript/revalidation until start()
     // to prevent unintended state transitions.