proxy-dumper: don't clean the target directory

I hope this should fix some of the issues we have with non-accessible cert files after updates

docker-compose.yml

@@ -33,10 +33,10 @@ services:
       file --watch --source /cert/acme.json --version v2 --domain-subdir
       --crt-name=fullchain --crt-ext=.pem
       --key-name=privkey --key-ext=.pem
+      --clean=false
       --post-hook "chmod -R a+r /ssl/"
       --dest /ssl
 
-
 networks:
   web:
     driver: bridge