fix: dockerfile for salt-lint version 0.3.0

Fix Dockerfile for salt-lint for version 0.3.0 by removing the version
pinning and only install salt-lint itself as SaltStack has been removed
as dependency.

Signed-off-by: Roald Nefs <info@roaldnefs.com>

docker/Dockerfile

@@ -1,21 +1,15 @@
 FROM python:3.7-alpine
 LABEL maintainer="info@warpnet.nl"
 
-# Install required alpine packages
-# hadolint ignore=DL3018,DL3019
-RUN apk add --no-cache gcc g++ build-base libzmq musl-dev zeromq-dev
-
 # Install the salt-lint package
-RUN pip install --no-cache salt-lint==v0.2.0
-
-# Remove development utilities
-RUN apk del --no-cache gcc g++ build-base libzmq musl-dev zeromq-dev \
- && rm -rf /var/cache/apk/*
+# hadolint ignore=DL3013
+RUN pip install --no-cache salt-lint
 
+# Create the linter user
 RUN addgroup -S -g 800 linter \
  && adduser -S -u 800 -S -H -D -G linter linter
 
 # Run as linter user
 USER linter
 
-CMD ["/usr/local/bin/salt-lint"]
+CMD ["/usr/local/bin/salt-lint"]