Bump Dockerfile version to 0.7.4

The previous version of the Dockerfile made use of version 0.7.3. However because of changes in dependencies, this can no longer be compiled from source. To fix this regression, this commit updates the version used to 0.7.4.

Dockerfile

@@ -3,7 +3,7 @@ FROM golang:1.14-alpine as dockergen
 RUN apk add --no-cache git
 
 # Download the sources for the given version
-ENV VERSION 0.7.3
+ENV VERSION 0.7.4
 ADD https://github.com/jwilder/docker-gen/archive/${VERSION}.tar.gz sources.tar.gz
 
 # Move the sources into the right directory
@@ -21,7 +21,7 @@ LABEL maintainer="Jason Wilder <mail@jasonwilder.com>"
 
 RUN apk -U add openssl
 
-ENV VERSION 0.7.3
+ENV VERSION 0.7.4
 COPY --from=dockergen /go/src/github.com/jwilder/docker-gen/docker-gen /usr/local/bin/docker-gen
 ENV DOCKER_HOST unix:///tmp/docker.sock