Yarn cache cleanup right after install in Docker (#23557)

Dockerfile

@@ -37,7 +37,8 @@ RUN apt-get update && \
     bundle config set --local without 'development test' && \
     bundle config set silence_root_warning true && \
     bundle install -j"$(nproc)" && \
-    yarn install --pure-lockfile --network-timeout 600000
+    yarn install --pure-lockfile --network-timeout 600000 && \
+    yarn cache clean
 
 FROM node:${NODE_VERSION}
 
@@ -91,8 +92,7 @@ USER mastodon
 WORKDIR /opt/mastodon
 
 # Precompile assets
-RUN OTP_SECRET=precompile_placeholder SECRET_KEY_BASE=precompile_placeholder rails assets:precompile && \
+RUN OTP_SECRET=precompile_placeholder SECRET_KEY_BASE=precompile_placeholder rails assets:precompile
-    yarn cache clean
 
 # Set the work dir and the container entry point
 ENTRYPOINT ["/usr/bin/tini", "--"]