Fix Typo in compose.yml file

remove duplicate "volume:"

Author: SabryTarek

satosa/compose.yml

@@ -50,7 +50,6 @@ services:
     networks:
       dev:
         ipv4_address: 172.16.25.102
-    volumes:
     volumes:
       - ../pysaml2-idp/etc/:/opt/pysaml2-idp/etc/
       - ../docker-satosa/etc/backend.xml:/opt/pysaml2-idp/etc/backend.xml:ro