zfsbootmenu-help: use cat in place of less

less-633, when invoked under fzf as a preview helper, does not render any
text. The previously known-good version of less was 608. Advanced
functionality such as searching or paging is not needed or even
functional in fzf.

GNU cat and Busybox cat preserve embedded ansi color styling.

Author: zdykstra

zfsbootmenu/install-helpers.sh

@@ -36,6 +36,7 @@ zfsbootmenu_essential_binaries=(
   "dmesg"
   "fzf"
   "setsid"
+  "cat"
 )
 
 # shellcheck disable=SC2034

zfsbootmenu/libexec/zfsbootmenu-help

@@ -80,7 +80,7 @@ while getopts "lL:s:" opt; do
       exit
       ;;
     s)
-      less -f -n -r "${OPTARG}"
+      cat "${OPTARG}"
       exit
       ;;
     ?)