@Vivian like Josh said there is no way to remove the link. In fact, there is no way to control anything once the user receives an email and forwards it on their own using their mail app. When you think about it, if you could control how the e-mail looks once it's forwarded, that would be akin to a sender stopping you from copying, pasting, quoting, etc. -- and the security implications would be terrifying.
(That said, some very restrictive "black box" mail apps, like the one on my old Blackberry, wouldn't let me change the body of a forwarded email even if I wanted to -- I could only prepend new introductory text. This was supposedly to guarantee an audit trail and was a recipe for frustration. New devices and computers let you keep the whole, part, or none of an original email when forwarding.)
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