refactor: change ordering of docker file

This means when there are test changes we wont have to rerun `npm ci`

Author: domharrington

__tests__/integrations/node.Dockerfile

@@ -9,6 +9,6 @@ RUN npm run build
 
 # Install top level dependencies
 WORKDIR /src
+ADD __tests__ /src/__tests__
 ADD package*.json /src/
 RUN npm ci
-ADD __tests__ /src/__tests__