MT#11387 Switch Pre-Depends on ngcp-system-tools to Depends

I can't find any reason why we should Pre-Depend on ngcp-system-tools.
Since piupart fails to run because of the Pre-Dependency let's try
switching to Depends instead.

Change-Id: Ic3e64f765ed2dd860d03bdbb02f6e7103da627d9

debian/control

@@ -8,8 +8,8 @@ Homepage: http://sipwise.com/
 
 Package: ngcp-db-schema
 Architecture: all
-Pre-Depends: ngcp-system-tools
-Depends: ${misc:Depends}
+Depends: ngcp-system-tools-ce | ngcp-system-tools,
+         ${misc:Depends}
 Description: database schema for Sipwise's NGCP platform
  This package provides the database schema for Sipwise's NGCP
  platform.