remove unnecessary dockerfile

.docker/make/alpine/Dockerfile

@@ -1,22 +0,0 @@
-FROM alpine:latest
-
-MAINTAINER Nikita Sobolev (mail@sobolevn.me)
-
-# Dependencies and project initialization:
-
-RUN apk add --no-cache --update \
-  man make git ruby ruby-dev bash ruby-bundler \
-  ca-certificates libressl libressl-dev build-base
-RUN mkdir /code
-
-# This will increase the container size, but speed up the build,
-# since this part will change, while the dependencies won't:
-
-WORKDIR /code
-
-# Removing `origin` for good:
-
-RUN git clone -q https://github.com/sobolevn/git-secret.git && \
-    cd git-secret && git remote rm origin
-
-WORKDIR /code/git-secret