postgresql-postgis2: Drop PGSQL_VERSIONS_ACCEPTED

Currently, this package builds with all versions of postgreqsl in
pkgsrc, and it is likely to do so in the future, so there is no need
for an explicit list.

databases/postgresql-postgis2/Makefile

@@ -1,4 +1,4 @@
-# $NetBSD: Makefile,v 1.48 2018/09/11 17:26:13 gdt Exp $
+# $NetBSD: Makefile,v 1.49 2018/09/23 15:38:00 gdt Exp $
 
 MAJOR=		2.4
 DISTNAME=	postgis-${MAJOR}.4
@@ -29,7 +29,6 @@ CONFLICTS=		postgis-[0-9]*
 # gmake complains about adding + to parent rule
 MAKE_JOBS_SAFE=		no
 
-PGSQL_VERSIONS_ACCEPTED=	96 95 94 93
 
 USE_GCC_RUNTIME=	yes
 USE_LANGUAGES=		c c++ c99