go.mod: bump github.com/stellar/go-xdr to a87d4d0 (#5938)

Picks up stellar/go-xdr#31, which enforces MaxInputLen at the io.Reader
boundary via io.LimitedReader. Decode semantics are unchanged for the
generated UnmarshalBinary path (bytes.Reader length already bounds reads
to len(inp)); microbenchmarks show a ~3% unmarshal overhead from the
added wrapping.

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: 2 people

go.mod

@@ -35,7 +35,7 @@ require (
 	github.com/spf13/cobra v1.7.0
 	github.com/spf13/pflag v1.0.5
 	github.com/spf13/viper v1.17.0
-	github.com/stellar/go-xdr v0.0.0-20260312225820-cc2b0611aabf
+	github.com/stellar/go-xdr v0.0.0-20260423131911-a87d4d0789c3
 	github.com/stretchr/testify v1.10.0
 	github.com/tyler-smith/go-bip39 v0.0.0-20180618194314-52158e4697b8
 	github.com/xdrpp/goxdr v0.1.1

go.sum

@@ -453,8 +453,8 @@ github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/spf13/viper v1.17.0 h1:I5txKw7MJasPL/BrfkbA0Jyo/oELqVmux4pR/UxOMfI=
 github.com/spf13/viper v1.17.0/go.mod h1:BmMMMLQXSbcHK6KAOiFLz0l5JHrU89OdIRHvsk0+yVI=
-github.com/stellar/go-xdr v0.0.0-20260312225820-cc2b0611aabf h1:GY1RVbX3Hg7poPXEf6yojjP0hyypvgUgZmCqQU9D0xg=
-github.com/stellar/go-xdr v0.0.0-20260312225820-cc2b0611aabf/go.mod h1:If+U9Z1W5xU97VrOgJandQT+2dN7/iOpkCrxBJEyF80=
+github.com/stellar/go-xdr v0.0.0-20260423131911-a87d4d0789c3 h1:/NnsQpfVYPFr5Xm/V7EOblI8P05zewwkJLOlLItsW7U=
+github.com/stellar/go-xdr v0.0.0-20260423131911-a87d4d0789c3/go.mod h1:If+U9Z1W5xU97VrOgJandQT+2dN7/iOpkCrxBJEyF80=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
 github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=