bounds-check against sk=1

+sign:schnorr crashes on `=(0 sk)`, so the bounds checking code is not
exercised for sk=0. It also crashes on `(gte sk n.domain.c)`, which is
redundant with the size check on sk, so we remove that.

pkg/arvo/sys/zuse.hoon

@@ -2265,7 +2265,6 @@
           ~/  %sosi
           |=  [sk=@I m=@I a=@I]
           ^-  @J
-          ?>  (gte 32 (met 3 sk))
           ?>  (gte 32 (met 3 m))
           ?>  (gte 32 (met 3 a))
           =/  c  curve

pkg/arvo/tests/sys/zuse/crypto/secp256k1.hoon

@@ -330,8 +330,8 @@
       ffff.ffff.ffff.ffff.ffff.ffff.ffff.ffff
   =/  cases-big-sec=(list case)
     :~  [too-big 0 0 0 0]
-        [0 0 too-big 0 0]
-        [0 0 0 too-big 0]
+        [1 0 too-big 0 0]
+        [1 0 0 too-big 0]
     ==
   =/  cases-big-pub=(list case)
     :~  [0 too-big 0 0 0]