CONTRIBUTING: Remove docs/README.md reference

Current ocitools docs for the man pages are under man/. No docs for
building them yet beyond the Makefile rule, and that may be all we
need ;).  Because there is no downstream consensus on doc locations,
remove the reference.  Downstream repositories can add it (or similar
content) back in as they see fit [1].  I don't expect a lot of churn
in this document, so there shouldn't be many conflicts between those
downstream changes and further project-template development.

[1]: opencontainers#4 (comment)

Signed-off-by: W. Trevor King <[email protected]>

Author: wking

CONTRIBUTING.md

@@ -34,8 +34,7 @@ before submitting a pull request.
 
 Update the documentation when creating or modifying features. Test
 your documentation changes for clarity, concision, and correctness, as
-well as a clean documentation build. See ``docs/README.md`` for more
-information on building the docs and how docs get released.
+well as a clean documentation build.
 
 Write clean code. Universally formatted code promotes ease of writing, reading,
 and maintenance. Always run `gofmt -s -w file.go` on each changed file before