docs: Remove a dangling "Please abide by" from CONTRIBUTING.md [ci skip]
docs: Remove a dangling "Please abide by" from CONTRIBUTING.md [ci skip]

It look like it probably preceded a link to the CoC in an earlier draft
of 8e469aa11bf7f6fe8e9afb56998f8055572cc005, but now it's just dangling.

octokit/octokit.rb,octokit/octokit.rb