macOS: Revert default Hi-DPI support in applications

This reverts commit v3.9.0-rc1~287^2 (macOS: Enable Hi-DPI support in
applications by default, 2017-04-08).  It breaks iOS applications that
do not use their own `MACOSX_BUNDLE_INFO_PLIST` because `NSApplication`
is only for macOS apps.  Until more complete support for iOS is added
to CMake (e.g. with a different default plist file) we must allow
our default plist file to work for both macOS and iOS.

Fixes: #17179
Status Job ID Name Coverage
passed ghostflow-branch-check-master

passed ghostflow-commit-check

passed ghostflow-stager