Generally you cannot, but you can replace it.
BUT, if it is a non-load-bearing wall, you don't need a header.
I'm guessing that the header you have was installed for the pocket door opening. But that doesn't mean you will need a header if you remove the wall altogether.
If you are not able to tell for sure if the wall is non-load-bearing, you will have to call in a pro. Either a structural engineer or an experienced contractor. Expect to pay a reasonable fee for the service since he may have to climb into the attic to tell.