Revert "IS-364: Bump Golang CI. (#14123)" (#14133)

This reverts commit 81d6ae2207.

build/Dockerfile.buildenv

@@ -1,3 +1,3 @@
-FROM golang:1.14.1
+FROM golang:1.13
 
 RUN apt-get update && apt-get install -y make git apt-transport-https ca-certificates curl software-properties-common build-essential zip xmlsec1 jq