Improve an error message.
Improve an error message.

Patch by: David Glasser <glasser@mit.edu>

* subversion/libsvn_wc/adm_ops.c
  (svn_wc_add2): Clarify node type change error message to not imply that the
  next step must be to "commit the deletion", which may have already occurred.

jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion,jmckaskill/subversion