[Code health] Remove two pdfium targets from no_check_targets

These were fixed for standalone PDFium at
  https://pdfium-review.googlesource.com/c/pdfium/+/73015

but still persist in Chromium's version of /.gn

Change-Id: I57fa0250a5a668935978988d949311d86f9bc244
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2640922Reviewed-by: Erik Staab <estaab@chromium.org>
Commit-Queue: Tom Sepez <tsepez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#845390}

.gn

@@ -193,9 +193,7 @@ no_check_targets = [
   "//third_party/openscreen/src/osp/public:*",  # 1 error
   "//third_party/openscreen/src/osp:*",  # 13 errors
   "//third_party/openscreen/src/util:*",  # 29 errors
-  "//third_party/pdfium/samples:*",  # 1 error
   "//third_party/pdfium/third_party:*",  # 2 errors
-  "//third_party/pdfium:*",  # 1 error
 
   # //v8/*, https://crbug.com/v8/7330
   "//v8/src/inspector:*",  # 20 errors