skinny: remove comment that matches field label (callState)

skinny: remove comment that matches field label (callState)

Fixes checkAPIs error:

    Error: the blurb for hf_skinny_callState ("CallState") matches the
    field name ("callState") in epan/dissectors/packet-skinny.c

Change-Id: Id12396eb101bf66e148aed95d5c773b90d06ff34
Fixes: v1.99.0-rc1-1511-g276a697a6b ("[RFC] Skinny: Rewrite using automatic code generation")
Reviewed-on: https://code.wireshark.org/review/29747
Reviewed-by: Anders Broman <a.broman58@gmail.com>