Adjust contract of create-archive-from-port to match documentation

[nxg]

Trivial change...

The documentation for create-archive-from-port says:

(create-archive-from-port  vault-name                        
                           port                              
                           description                       
                          [#:part-size part-size]) -> string?
  vault-name : string?                                       
  port : input-port?                                         
  description : string?                                      
  part-size : exact-nonnegative-integer? = (* 1024 1024)

This suggests that keyword #:part-size is optional, but the original contract requires it to be present.

[greghendershott]

Ah. Good catch. Thank you.