Docker: Fix "Failed export and unexpected container restart"

- Fixes #4089

Also this was broken too:

docker-compose exec wekandb apt-get update

because /tmp didn't exist, it was introduced by this commit:
1322c1fbbd

.devcontainer/Dockerfile

@@ -236,7 +236,7 @@ RUN \
     set -o xtrace && \
     apt-get clean -y && \
     apt-get autoremove -y && \
-    rm -Rf /tmp* && \
+    rm -Rf /tmp/* && \
     rm -Rf /home/wekan/app_build && \
     rm -Rf /var/cache/apt /var/lib/apt/lists && \
     rm -Rf /var/lib/apt/lists/*