Revert "build: Go 1.14 for the Debian etc builds"

This reverts commit d400e5142287e647786c18eb6cc8a6a3f55183d3.

Dockerfile.builder

@@ -1,5 +1,5 @@
 # We will grab the Go compiler from the latest Go image.
-FROM golang:1.14 as go
+FROM golang:1.13 as go
 
 # Otherwise we base on the snapcraft container as that is by far the
 # most complex and tricky thing to get installed and working...