yarn is okay as is with newer node

Author: tsmathis

mpcontribs-portal/Dockerfile

@@ -6,9 +6,7 @@ FROM node AS webpack-deps
 RUN apt-get update && apt-get install -y --no-install-recommends \
   git curl gnupg ca-certificates apt-transport-https \
   && apt-get clean
-RUN curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add -
-RUN echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list
-RUN apt-get update && apt-get install -y --no-install-recommends yarn
+RUN npm install -g yarn
 ENV NODE_ENV production
 WORKDIR /app
 COPY package.json .