Fix Google3 build by updating pdf path after https://codereview.chromium.org/1781773002

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1802553003

Review URL: https://codereview.chromium.org/1802553003
diff --git a/public.bzl b/public.bzl
index 2b07a30..f647635 100644
--- a/public.bzl
+++ b/public.bzl
@@ -94,7 +94,7 @@
 
         # Exclude multiple definitions.
         # TODO(mtklein): Move to opts?
-        "src/doc/SkDocument_PDF_None.cpp",  # We use SkDocument_PDF.cpp.
+        "src/pdf/SkDocument_PDF_None.cpp",  # We use src/pdf/SkPDFDocument.cpp.
         "src/gpu/gl/GrGLCreateNativeInterface_none.cpp",
         "src/gpu/gl/GrGLDefaultInterface_native.cpp",
         "src/gpu/gl/GrGLDefaultInterface_none.cpp",