Remove Skia Sfntly dependency

Skia no longer supports use of Sfntly as a font subsetter, remove this
unused mention to clarify this.

Change-Id: I08ce184bf3a75de45f4fcc1917719964669514ce
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/117690
Commit-Queue: Ben Wagner <bungeman@google.com>
Reviewed-by: Ben Wagner <bungeman@google.com>
Reviewed-by: Lei Zhang <thestig@chromium.org>

skia/BUILD.gn

diff --git a/skia/BUILD.gn b/skia/BUILD.gn
index 8e6c586..2e9065f 100644
--- a/skia/BUILD.gn
+++ b/skia/BUILD.gn
@@ -360,7 +360,6 @@
   }
 
   if (skia_support_pdf) {
-    deps += [ "//third_party/sfntly" ]
     sources += skia_pdf_sources
   } else {
     sources += [ "//third_party/skia/src/pdf/SkDocument_PDF_None.cpp" ]