pager: remove obsolete comment

The comment at the top of pager.c claims that we've split
the code out so that Windows can do something different.
This dates back to f67b45f8 (Introduce trivial new pager.c
helper infrastructure, 2006-02-28), because the original
implementation used fork(). Later, we ended up sticking the
Windows #ifdefs into this file anyway. And then even later,
in ea27a18c (spawn pager via run_command interface,
2008-07-22) we unified the implementations.

So these days this comment is really saying nothing at all.
Let's drop it.
Signed-off-by: NJeff King <peff@peff.net>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

pager.c

@@ -6,11 +6,6 @@
 #define DEFAULT_PAGER "less"
 #endif
 
-/*
- * This is split up from the rest of git so that we can do
- * something different on Windows.
- */
-
 static struct child_process pager_process = CHILD_PROCESS_INIT;
 
 static void wait_for_pager(int in_signal)