ntp: don't care about changes to home page pref
ntp: don't care about changes to home page pref

a long while back the NTP showed some sort of UI depending on whether it was your home page or not, but that's long since gone so we don't need to reconstruct the cache if it's changed.

BUG=none
TEST=none


Review URL: http://codereview.chromium.org/8774014

git-svn-id: de016e52bd170d2d4f2344f9bf92d50478b649e0@112957 0039d316-1c4b-4281-b951-d872f2087c98

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