[base] Don't DCHECK GetCurrentThreadPriority() at the end of SetCurrentThreadPriority().

The DCHECK passes most of the time, but not always. It is inherently
racy, as external code could change the thread priority between when
we set it and when we DCHECK it. Removing it as the failures are
not actionnable.

Bug: 1044882
Change-Id: I0adb7a801c10fb15ada3ed229175fb08c0232b8f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2031705Reviewed-by: Gabriel Charette <gab@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#737483}

base/threading/platform_thread_win.cc

@@ -384,8 +384,6 @@ void PlatformThread::SetCurrentThreadPriorityImpl(ThreadPriority priority) {
       internal::AssertMemoryPriority(thread_handle, MEMORY_PRIORITY_VERY_LOW);
     }
   }
-
-  DCHECK_EQ(GetCurrentThreadPriority(), priority);
 }
 
 // static