[Formatting] `if (` -> `if(` in CMakeLists.txt (#35343)
Summary:
Same to `else`, `endif` and `elseif`.
Also prefer lowercase over uppercase ones
Pull Request resolved: https://github.com/pytorch/pytorch/pull/35343
Test Plan: None at all
Differential Revision: D20638789
Pulled By: malfet
fbshipit-source-id: 8058075693185e66f5dda7b825b725e139d0d000
