Update changelog for 7.9.1
Update changelog for 7.9.1

mParticle/mparticle-apple-sdk,mParticle/mparticle-apple-sdk,mParticle/mparticle-apple-sdk,mParticle/mParticle-iOS-SDK,mParticle/mParticle-iOS-SDK,mParticle/mparticle-apple-sdk,mParticle/mparticle-apple-sdk,mParticle/mParticle-iOS-SDK,mParticle/mparticle-apple-sdk