Update the identity of the response team for CoC violation reporting.

[benjyw]

The previous link was to a nonexistent doc, and in any case implied
that all "active committers" (not a currently official status)
were on the response team.

Instead we have designated a subset of the maintainers for this
purpose. All these maintainers, and only them, are members of
pants-conduct@.

[ci skip-rust]

[ci skip-build-wheels]

[jsirois]

Having served on one incident response, I think it's best I let others take up future incident responses. I'd like to step down from this list.

[cczona]

Please add @baroquebobcat back to the list. She's kindly agreed to stay on the response team for a while longer. Many thanks, Nora!

[cczona]

Ping.