[ntuple] remove redundant default inits for RFieldDescriptor members
[ntuple] remove redundant default inits for RFieldDescriptor members

root-mirror/root,karies/root,karies/root,olifre/root,karies/root,olifre/root,karies/root,olifre/root,karies/root,root-mirror/root,karies/root,olifre/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,root-mirror/root,olifre/root,olifre/root,karies/root,karies/root,root-mirror/root,root-mirror/root,root-mirror/root,karies/root,root-mirror/root,karies/root,olifre/root,olifre/root,root-mirror/root,root-mirror/root,karies/root