Improving docs' coherence

[akashagarwal7]

https://github.com/a2i2/surround/blob/a7638b0d000df048267e2a9e09bf67e1b5b86493/surround/stage.py#L43-L69

This is a very small suggestion—it'd be less confusing for someone like me who is new to ML and the Surround project, if in the above snippet used a single term everywhere, i.e. Predict instead of Estimate and Predict, assuming they don't hold different meanings in the ML land/this context. 🙂