less.sh: Avoid unnecessary stat call

While at it, remove unnecessary executable bits (in git) and shebang
from less.*sh.

less.csh

@@ -1,4 +1,3 @@
-#!/bin/csh
 # less initialization script (csh)
 if ( -x /usr/bin/lesspipe.sh ) then
     if ( $?LESSOPEN && { eval 'test ! -z "$LESSOPEN"' } ) then

less.sh

@@ -1,4 +1,4 @@
 # less initialization script (sh)
-if [ -x /usr/bin/lesspipe.sh ] && [ -z "$LESSOPEN" ]; then
+if [ -z "$LESSOPEN" ] && [ -x /usr/bin/lesspipe.sh ]; then
     export LESSOPEN="|/usr/bin/lesspipe.sh %s"
 fi