component_updater: remove dubious CHECK.

It's not clear that such an invariant can be enforced. There could be
an issue cleaning up BITS files but can't assert on such runtime
condition.

(cherry picked from commit c25477e)

Fixed: 1427446
Change-Id: I91dce63e50f28ad63360bbc1a06fbd9760930457
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4369790
Auto-Submit: Sorin Jianu <sorin@chromium.org>
Commit-Queue: Sorin Jianu <sorin@chromium.org>
Reviewed-by: Joshua Pawlicki <waffles@chromium.org>
Commit-Queue: Joshua Pawlicki <waffles@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1121944}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4374739
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Sorin Jianu <sorin@chromium.org>
Owners-Override: Prudhvikumar Bommana <pbommana@google.com>
Commit-Queue: Prudhvikumar Bommana <pbommana@google.com>
Auto-Submit: Prudhvikumar Bommana <pbommana@google.com>
Cr-Commit-Position: refs/branch-heads/5672@{#38}
Cr-Branched-From: 5f2a724-refs/heads/main@{#1121455}

components/update_client/background_downloader_win.cc

@@ -577,8 +577,6 @@ void BackgroundDownloader::EndDownload(HRESULT error) {
 
   const int error_to_report = SUCCEEDED(error) ? 0 : error;
 
-  CHECK(static_cast<bool>(error_to_report) == !base::PathExists(response_));
-
   DownloadMetrics download_metrics;
   download_metrics.url = url();
   download_metrics.downloader = DownloadMetrics::kBits;