Fix potential use after move in Differentiator (#36537)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/36537

##Changelog:
[Internal] -

This popped up when I was landing D44172494.

Order of arguments evaluation to a function call in C++ is unspecified, therefore there was  a potential danger of use after move in two places in `Differentiator.cpp`

This diff fixes it.

Reviewed By: javache

Differential Revision: D44215210

fbshipit-source-id: 828ca379e2ba5a40506f1ff3136150af63ea1ff7