Clean up unused createStoreOwnPropertyInst

Summary:
We have 4 diferent versions of createStoreOwnPropertyInst, defined in different places in IRBuilder.h.
Only 2 are used and one of them only has one occurance. Those definitions seem unnecessary to me and only increase the complexity of the API.
Clean them up

Reviewed By: dulinriley

Differential Revision: D16496423

fbshipit-source-id: 0eba772aac774921d4fcd4463cdfa5f96db4ea83

Initial commit

fbshipit-source-id: 75e378602933ab4aa91677dfa509a67063e64516