cue: use v2 of abitrary precision decimal package

This fixes a major bug that currently does not
affect cue but is dangerous to let linger.

Change-Id: Ibd3e7581fa1fc399aa0ad45cb3f0bb30e334b034
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/2363
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>
diff --git a/go.sum b/go.sum
index 1bc59e3..d53173b 100644
--- a/go.sum
+++ b/go.sum
@@ -1,5 +1,7 @@
 github.com/cockroachdb/apd v1.1.0 h1:3LFP3629v+1aKXU5Q37mxmRxX/pIu1nijXydLShEq5I=
 github.com/cockroachdb/apd v1.1.0/go.mod h1:8Sl8LxpKi29FqWXR16WEFZRNSz3SoPzUzeMeY4+DwBQ=
+github.com/cockroachdb/apd/v2 v2.0.1 h1:y1Rh3tEU89D+7Tgbw+lp52T6p/GJLpDmNvr10UWqLTE=
+github.com/cockroachdb/apd/v2 v2.0.1/go.mod h1:DDxRlzC2lo3/vSlmSoS7JkqbbrARPuFOGr0B9pvN3Gw=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/emicklei/proto v1.6.11 h1:KZHE0+iwVLth2D/K8jat9rs70K6TFWyol8ihrOdrbM0=
 github.com/emicklei/proto v1.6.11/go.mod h1:rn1FgRS/FANiZdD2djyH7TMA9jdRDcYQ9IEN9yvjX0A=