I don't believe it.
2 seconds sound clip from the The Shootist movie soundboard.
You can hear this line at 00:45:36.993 in the DVD version of the movie.
Quote context
[...]
- I will not have that language in my house.
- Sorry, but this is a great day. Our house is a part of history now. You've got to know that.
- That is nothing to be proud of.
- Gillom! All right! It's time you knew. He's dying.
- Who?
- You're lying. He would have told me.
- But he didn't tell you! He told me. He's dying.
- Ma. Ma.
[...]