Remove redundant entries in pdf/BUILD.gn.

Headers do not needed to be repeated in the public and sources sections.

Change-Id: Id308f418cf1a9e74f7e57c59bc4ef9898d440b9a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2036260Reviewed-by: Daniel Hosseinian <dhoss@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#738018}

pdf/BUILD.gn

@@ -67,11 +67,9 @@ if (enable_pdf) {
       "paint_manager.cc",
       "paint_manager.h",
       "pdf.cc",
-      "pdf.h",
       "pdf_engine.cc",
       "pdf_engine.h",
       "pdf_ppapi.cc",
-      "pdf_ppapi.h",
       "pdf_transform.cc",
       "pdf_transform.h",
       "preview_mode_client.cc",