looks like it is in this macro:
/nav_to.do?uri=sys_ui_macro.do?sys_id=b74cff91c30031000096dfdc64d3ae65
look at that file starting around line 24. but this is already only shown if showHistory is marked true. This comes from the KBViewModelSNC script include. You could consider overriding the _populateAdditionalInformation() function in the KBViewModel script include. that is where you can override default behaviors in the first mentioned script include.
Otherwise, you could consider customizing the macro I posted above to remove it, but then you are going to have upgrade conflicts.
Perhaps the easiest way to remove it would be to add this css
#versionNumber {
display: none;
}
to this style sheet:
/nav_to.do?uri=content_css.do?sys_id=b3ba3821d73221004792a1737e610382
