insane: remove unsafe-references-in-scripts check

insane: remove unsafe-references-in-scripts check

We've already removed unsafe-references-in-binaries (which was fundamentally
broken) and nobody really cares about / and /usr being on different filesystems
anymore (at least if they, they're keeping very quiet and not fixing the bugs).

As this test was a minor detail in the scope of supporting separate / and /usr
which we don't support, it can be removed.

(From OE-Core rev: 5363a5e43462e22ed61e87923e00657b740f6823)

Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>