Mark PFIncrementalStore as deprecated.

I've deprecated the pod as functionality is now provided by parent service. See repo for reference: https://github.com/sbonami/PFIncrementalStore
Utilize deprecated_in_favor_of rather than deprecated

To better point users to the new Parse pod, utilize `deprecated_in_favor_of` rather than just `deprecated`.
Bump iOS platform dependency to meet Parse minimum
Merge pull request #12857 from sbonami/patch-2

[update] Mark PFIncrementalStore as deprecated.