swh-counters/Dockerfile: Use proper ENV instruction

apps/swh-counters/Dockerfile

@@ -24,10 +24,10 @@ COPY --chmod=0755 entrypoint.sh ${workdir}
 
 USER ${user}
 ENV SWH_CONFIG_FILENAME=${configdir}/config.yml
-ENV PORT 5011
+ENV PORT=5011
 EXPOSE $PORT
-ENV THREADS 2
-ENV WORKERS 2
-ENV TIMEOUT 3600
+ENV THREADS=2
+ENV WORKERS=2
+ENV TIMEOUT=3600
 
 ENTRYPOINT ["/opt/swh/entrypoint.sh"]