Bug 907404: disable the in-product whatsnew page, so that manual upgrades are consistent with updater upgrades wrt showing the whatsnew page (updater upgrades disable whatsnew via snippets), r=dolske, a=asa

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extra : transplant_source : %0D6A%BEP%99%09%CEVA%00l%A7%27%C3%08%EF%03%03%82