update contribute.html for regression testing

[Jeffrey A Law]

  In message < 200011071715.JAA26585@racerx.synopsys.com >you write:
  > 
  > > Someone also needs to look at the instructions in the info manual
  > > (gcc.texi) on sending patches (e.g. sending each logically separate patch
  > > separately), merge them into contribute.html and make the info manual
  > > point to contribute.html.
  > 
  > Yet another reason to do everything in texinfo and use texi2html to
  > generate the web pages.
Agreed.

jeff