bsdinstall: allow ZFS root on GPT under UEFI (amd64)

GPT+ZFS+UEFI boots fine, but the manual guided
wizard prevented it.

MFC after: 3 days

Reviewed by:	imp, adrian
Differential Revision:	https://reviews.freebsd.org/D59603

usr.sbin/bsdinstall/partedit/partedit_x86.c

@@ -84,8 +84,7 @@ is_fs_bootable(const char *part_type, const char *fs)
 		return (1);
 
 	if (strcmp(fs, "freebsd-zfs") == 0 &&
-	    strcmp(part_type, "GPT") == 0 &&
-	    strcmp(x86_bootmethod(), "BIOS") == 0)
+	    strcmp(part_type, "GPT") == 0)
 		return (1);
 
 	return (0);