Fix symlink to Pods-acknowledgements.plist

Currently one can't use this pod because it breaks the build of app. The problem is that the simlink to `Pods-acknowledgements.plist` is broken. (I think CocoaPods' inner folder hierarchy has changed in the meantime.) This PR fixes that.

However it seems that the pod does not pass the `pod lib lint` check since there is no Pods-acknowledgements.plist yet so the simlink is broken (independently from this PR). Maybe earlier it wasn't an error if your pod contained a broken simlink.

So I'm not sure that you can update the pod but I hope. :)