Remove which command from default image

* This was a script relying on a working /etc/profile, which may not be
there
 * Instead, use GNU which, available as an haikuport recipe
 * Since the command does not seem to be needed for Haiku to run (and
also because I don't know how to do it), GNU which isn't in the default
 install.
 * Typing "which" in a terminal still works, as that uses an alias
defined directly in /etc/profile.

data/bin/which

@@ -1,6 +0,0 @@
-#!/bin/bash
-
-. /etc/profile > /dev/null 2>&1
-
-whence $*
-