ci: reorder Dockerfile for efficiency

Dockerfile

@@ -6,14 +6,14 @@ WORKDIR ${HOME}
 
 ENV NODE_ENV "development"
 
+# Install dependencies for Cypress
+RUN apt-get -y update && apt-get -y install xvfb libgtk-3-dev libnotify-dev libgconf-2-4 libnss3 libxss1 libasound2
+
 COPY . .
 
 # We do a development install because react-styleguidist is a dev dependency and we want to run tests
 RUN [ "yarn", "install", "--frozen-lockfile" ]
 
-# Install dependencies for Cypress
-RUN apt-get -y update && apt-get -y install xvfb libgtk-3-dev libnotify-dev libgconf-2-4 libnss3 libxss1 libasound2
-
 ENV NODE_ENV ${NODE_ENV}
 
 RUN [ "npx", "pubsweet", "build"]