remove yarn

Dockerfile

@@ -23,10 +23,7 @@ RUN echo 'debconf debconf/frontend select Noninteractive' | debconf-set-selectio
         rsync \
         ssh \
         wget \
-    && curl -sS https://dl.yarnpkg.com/debian/pubkey.gpg | apt-key add - \
-    && echo "deb https://dl.yarnpkg.com/debian/ stable main" | tee /etc/apt/sources.list.d/yarn.list \
     && apt-get update \
-    && apt-get install yarn -y \
     && apt-get clean \
     && rm -r /var/lib/apt/lists/*