Delete redundant CODE_OF_CONDUCT.md

The Code of Conduct is set in the enterprise-contract organization -
https://github.com/enterprise-contract/.github/blob/main/CODE_OF_CONDUCT.md
That applies to all repositories within the organization.

The CODE_OF_CONDUCT.md file in this repo overrides the org version,
though they are identical.  Delete it so that the org version will be
used.

Author: Acepresso