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

src/shared/pager.c

@@ -131,7 +131,8 @@ int pager_open(PagerFlags flags) {
         if (flags & PAGER_JUMP_TO_END)
                 less_opts = strjoina(less_opts, " +G");
 
-        r = safe_fork("(pager)", FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_RLIMIT_NOFILE_SAFE|FORK_LOG, &pager_pid);
+        /* We set SIGINT as PR_DEATHSIG signal here, to match the "K" parameter we set in $LESS, which enables SIGINT behaviour. */
+        r = safe_fork("(pager)", FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGINT|FORK_RLIMIT_NOFILE_SAFE|FORK_LOG, &pager_pid);
         if (r < 0)
                 return r;
         if (r == 0) {