fix: Add Foundation import to IterbaleMPHelper.h file

[mmustafa-tse]

Summary

• Customer reported that they ran into a build error that looks like it needs to be fixed in the Iterable kit by adding import foundation to IterableMPHelper.h file. Here is a Gist of the build error: https://gist.github.com/tguidon/b732de9669b38be805ddfb90d12abf28

Testing Plan

• Was this tested locally? If not, explain why.
• N/A

Reference Issue (For mParticle employees only. Ignore if you are an outside contributor)

• Closes https://rokt.atlassian.net/browse/SDKE-862