Revert of Remove CPDF_Object::Release() in favor of direct delete (patchset #11 id:200001 of https://codereview.chromium.org/2384883003/ )

Reason for revert:
Looks like it's blocking the roll.

https://build.chromium.org/p/tryserver.chromium.linux/builders/linux_chromium_compile_dbg_ng/builds/186619

Original issue's description:
> Remove CPDF_Object::Release() in favor of direct delete
>
> Follow-on once we prove Release always deletes in previous CL.
>
> Committed: https://pdfium.googlesource.com/pdfium/+/4de3d095c9d9e961f93750cf1ebd489fd515be12

TBR=thestig@chromium.org,tsepez@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Review-Url: https://codereview.chromium.org/2478253002
diff --git a/fpdfsdk/fpdfdoc_unittest.cpp b/fpdfsdk/fpdfdoc_unittest.cpp
index 39e81d5..408d2fa 100644
--- a/fpdfsdk/fpdfdoc_unittest.cpp
+++ b/fpdfsdk/fpdfdoc_unittest.cpp
@@ -87,7 +87,7 @@
  protected:
   std::unique_ptr<CPDF_TestPdfDocument> m_pDoc;
   CPDF_IndirectObjectHolder* m_pIndirectObjs;
-  std::unique_ptr<CPDF_Dictionary> m_pRootObj;
+  std::unique_ptr<CPDF_Dictionary, ReleaseDeleter<CPDF_Dictionary>> m_pRootObj;
 };
 
 TEST_F(PDFDocTest, FindBookmark) {