Replace base/task/ temporary forward headers with their final locations

Note to QA: This merely changes includes and should not be blamed
for files it touched.

Bug: 1255932
Change-Id: I1ce4e31efd5792ebf2080812e665cae838a54972
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3226943
Reviewed-by: Gabriel Charette <gab@chromium.org>
Owners-Override: Gabriel Charette <gab@chromium.org>
Cr-Commit-Position: refs/heads/main@{#932153}

diff --git a/gpu/ipc/service/gpu_channel_manager.h b/gpu/ipc/service/gpu_channel_manager.h
index 9ab8728..efa8302 100644
--- a/gpu/ipc/service/gpu_channel_manager.h
+++ b/gpu/ipc/service/gpu_channel_manager.h

@@ -17,7 +17,7 @@
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
 #include "base/process/process_handle.h"
-#include "base/task/single_thread_task_runner_forward.h"
+#include "base/task/single_thread_task_runner.h"
 #include "base/threading/thread_checker.h"
 #include "base/unguessable_token.h"
 #include "build/build_config.h"