This is on the xda forum, though some of the suggestions for editing the build.prop file are more complicated. YMMV and you may brick your phone.
I opened /system/build.prop in Root Explorer in r/w mode, selected text editor, edited the line below (changed 231334 to 264707), then saved it. That's all. Root Explorer makes a backup build.prop file automatically
ro.build.fingerprint=verizon_wwe/inc/inc/inc:2.2/FRF91/264707:user/release-keys
Rebooted twice and no more nag.
Edit: I'm on Skyraider 3.3.3
I opened /system/build.prop in Root Explorer in r/w mode, selected text editor, edited the line below (changed 231334 to 264707), then saved it. That's all. Root Explorer makes a backup build.prop file automatically
ro.build.fingerprint=verizon_wwe/inc/inc/inc:2.2/FRF91/264707:user/release-keys
Rebooted twice and no more nag.
Edit: I'm on Skyraider 3.3.3