cmd/goyacc: remove empty branch

Found with honnef.co/go/tools/cmd/staticcheck.

Change-Id: I39e23936e01543db62b7b0919a3b58b65cd40099
Reviewed-on: https://go-review.googlesource.com/38174
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
1 file changed