You can refuse (and then go set your PSP to pretend it's on higher so the game runs) so it's not an issue even if it does happen.
Then in the VSH menu (press select on the PSP home screen and go to the configuration) there should be a setting somewhere to "use version.txt", set it to true.release:6.60:
build:5455,0,3,1,0:builder@vsh-build6
system:57716@release_660,0x06060010:
vsh6616@release_660,v58533@release_660,20110727:
target:1:WorldWide