[LSC] Add LOCAL_LICENSE_KINDS to external/Reactive-Extensions/RxCpp am: 6e6c469a7c am: c17d041feb am: 234f2f2fda

Original change: https://android-review.googlesource.com/c/platform/external/Reactive-Extensions/RxCpp/+/1588615

MUST ONLY BE SUBMITTED BY AUTOMERGER

Change-Id: I906b59b539b50656a19267ed9cd8f681c56d0859