Don't require boolp in signed.v

Author: proux01

theories/signed.v

@@ -1,7 +1,6 @@
 (* mathcomp analysis (c) 2017 Inria and AIST. License: CeCILL-C.              *)
 From Coq Require Import ssreflect ssrfun ssrbool.
 From mathcomp Require Import ssrnat eqtype choice order ssralg ssrnum ssrint.
-Require Import boolp.
 
 (******************************************************************************)
 (* This file develops tools to make the manipulation of numbers with a known  *)