chore: remove docker hub badge

Until whatever steps necessary are taken to fix automated docker builds, the badge isn't really helpful here.

README.md

@@ -4,7 +4,7 @@ Track your .proto files and prevent changes to messages and services which impac
 
 [![CircleCI](https://circleci.com/gh/nilslice/protolock/tree/master.svg?style=svg)](https://circleci.com/gh/nilslice/protolock/tree/master)
 [![GoDoc](https://img.shields.io/badge/godoc-reference-blue.svg?style=flat)](https://godoc.org/github.com/nilslice/protolock)
-[![Docker](https://img.shields.io/docker/cloud/build/nilslice/protolock.svg)](https://hub.docker.com/r/nilslice/protolock)
+
 ## Why
 
 Ever _accidentally_ break your API compatibility while you're busy fixing problems? You may have forgotten to reserve the field number of a message or you re-ordered fields after removing a property. Maybe a new team member was not familiar with the backward-compatibility of Protocol Buffers and made an easy mistake.