Requirements management plan at high level handles how requirements are analyzed , documented and managed. Changes are part of any project, so we can expect requirements to change during project life Cycle. When there are changes, you need to plan how those changes will be handled, hence you need to mention about configuration management activities.

Read Page 109 of PMBoK 5th Edition, it says, configuration management activities in Requirements plan will outline how product changes will be initiated, analyzed, tracked , reported and approved.

Hope this clarifies

Here is the video on this subject you may like to refer to..
https://www.youtube.com/watch?v=qp59GR5SZ3A

This is a great reference for future use. Thank you