Remove two unused WebKit2 PDF-related preferences
https://bugs.webkit.org/show_bug.cgi?id=136441

Reviewed by Dan Bernstein.

* Shared/WebPreferencesDefinitions.h:
Move the macro arguments comment down near where the macros are being used.
No need to check both PLATFORM(IOS) and PLATFORM(IOS_SIMULATOR); the second can't be true without the first.
These two PDF preferences are long-unused; if we bring back their functionality,
we'll bring back the preferences.


git-svn-id: http://svn.webkit.org/repository/webkit/trunk@173165 268f45cc-cd09-0410-ab3c-d52691b4dbfc