Fix docker image

Dockerfile

@@ -74,7 +74,7 @@ CMD ["/usr/local/bin/aleksis-docker-startup"]
 FROM core as assets
 RUN eatmydata aleksis-admin yarn install; \
     eatmydata aleksis-admin write_webpack_entrypoints; \
-    yarn run webpack; \
+    yarnpkg run webpack; \
     eatmydata aleksis-admin collectstatic --no-input; \
     rm -rf /usr/local/share/.cache
 
@@ -122,7 +122,7 @@ ONBUILD RUN set -e; \
             fi; \
             eatmydata aleksis-admin yarn install; \
             eatmydata aleksis-admin write_webpack_entrypoints; \
-            yarn run webpack; \
+            yarnpkg run webpack; \
             eatmydata aleksis-admin collectstatic --no-input; \
             rm -rf /usr/local/share/.cache; \
             eatmydata apt-get remove --purge -y yarnpkg $BUILD_DEPS; \