codegen: pass the context to ancillary_prefix in the table codec

The oneof support added to the table codec calls ancillary_prefix, which takes the codegen context as its first argument on this branch.

Author: iainmcgin

buffa-codegen/src/table_codec.rs

@@ -453,6 +453,7 @@ impl Oneofs {
         }
         Ok(Self {
             prefix: ancillary_prefix(
+                scope.ctx,
                 AncillaryKind::Oneof,
                 scope.current_package,
                 scope.proto_fqn,