ime: Remove unused statement and include.

It does not affect the test because SystemDecoder runs in a separate
process, so setting the fake main entry does not affect SystemDecoder.

Bug: 1148157
Change-Id: I99b5fac2da26be833f76063becbf586578d2965f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2537253Reviewed-by: My Nguyen <myy@chromium.org>
Commit-Queue: Darren Shen <shend@chromium.org>
Cr-Commit-Position: refs/heads/master@{#827696}

chrome/browser/chromeos/input_method/native_input_method_engine_browsertest.cc

@@ -25,7 +25,6 @@
 #include "chrome/test/base/ui_test_utils.h"
 #include "chromeos/constants/chromeos_features.h"
 #include "chromeos/constants/chromeos_pref_names.h"
-#include "chromeos/services/ime/decoder/system_engine.h"
 #include "components/autofill/core/browser/autofill_test_utils.h"
 #include "components/autofill/core/browser/data_model/autofill_profile.h"
 #include "components/autofill/core/browser/personal_data_manager.h"
@@ -150,7 +149,6 @@ class NativeInputMethodEngineTest : public InProcessBrowserTest,
 
  protected:
   void SetUp() override {
-    ime::FakeEngineMainEntryForTesting(nullptr);
     mojo::core::Init();
     InProcessBrowserTest::SetUp();
     ui::IMEBridge::Initialize();