Remove addt'l info (dead link) from PR template.

Main link is widely inclusive of information already.

Signed-off-by: H Dub <14808878+hdub-tech@users.noreply.github.com>

Author: hdub-tech

.github/PULL_REQUEST_TEMPLATE.md

@@ -4,9 +4,6 @@ https://github.com/docker/cli/blob/master/CONTRIBUTING.md
 
 ** Make sure all your commits include a signature generated with `git commit -s` **
 
-For additional information on our contributing process, read our contributing
-guide https://docs.docker.com/opensource/code/
-
 If this is a bug fix, make sure your description includes "fixes #xxxx", or
 "closes #xxxx"