pager: set PR_DEATHSIG for pager to SIGINT rather than SIGTERM

pager: set PR_DEATHSIG for pager to SIGINT rather than SIGTERM

"less" doesn't properly reset its terminal on SIGTERM, it does so only
on SIGINT. Let's thus configure SIGINT instead of SIGTERM.

I think this is something less should fix too, and clean up things
correctly on SIGTERM, too. However, given that we explicitly enable
SIGINT behaviour by passing "K" to $LESS I figure it makes sense if we
also send SIGINT instead of SIGTERM to match it.

Fixes: #16084