fix: dockerfile (#670)

## fixes docker image

Sorry, while reviewing the node refactoring, I wasn't paying enough
attention to the docker image. The root folder for the chain specs
changed. This should also be reflected by the docker file.

Dockerfile

@@ -30,7 +30,7 @@ USER node
 EXPOSE 30333 9933 9944
 VOLUME ["/data"]
 
-COPY ./dev-specs /node/dev-specs
+COPY ./chainspecs /node/chainspecs
 
 ENTRYPOINT ["/usr/local/bin/node-executable"]
 CMD ["--help"]