[DF][NFC] Rename TMinReturnType -> RMinReturnType
[DF][NFC] Rename TMinReturnType -> RMinReturnType

To respect the new naming conventions.

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