[Jobs API]: Clean up deprecate functions in gin.

This CL removes Jobs deprecated function overrides in gin:
IsRunning()
IsCompleted()

Change-Id: Ib7b39c4004bf2429e4e4a585062a8fbabfe54c16
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2638334Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Etienne Pierre-Doray <etiennep@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845246}

gin/v8_platform.cc

@@ -325,10 +325,6 @@ class JobHandleImpl : public v8::JobHandle {
   bool IsActive() override { return handle_.IsActive(); }
   bool IsValid() override { return !!handle_; }
 
-  // TODO(etiennep): Cleanup once rename is complete.
-  bool IsCompleted() override { return !IsActive(); }
-  bool IsRunning() override { return IsValid(); }
-
  private:
   static base::TaskPriority ToBaseTaskPriority(v8::TaskPriority priority) {
     switch (priority) {