Move start scripts to parent folder

There was only one start script per folder anyway, no need to keep the
structure so complicated

extras/docker/production/Dockerfile

@@ -64,9 +64,9 @@ COPY --from=builder --chown=wger:wger /home/wger/src/wger/core/static/yarn /home
 COPY ${DOCKER_DIR}/settings.py /home/wger/src
 COPY ${DOCKER_DIR}/settings.py /tmp/
 COPY ${DOCKER_DIR}/entrypoint.sh /home/wger/entrypoint.sh
-COPY ${DOCKER_DIR}/celery/beat/start /start-beat
-COPY ${DOCKER_DIR}/celery/worker/start /start-worker
-COPY ${DOCKER_DIR}/celery/flower/start /start-flower
+COPY ${DOCKER_DIR}/celery/start-beat /start-beat
+COPY ${DOCKER_DIR}/celery/start-worker /start-worker
+COPY ${DOCKER_DIR}/celery/start-flower /start-flower
 RUN chmod +x /home/wger/entrypoint.sh \
     && chmod +x /start-beat \
     && chmod +x /start-worker \