There isn't, and quite intentionally.
Telnet is a obviously a very insecure protocol, completely insecure in fact, and we strongly want to discourage usage.
Yet, it would be quite trivial to write a connection plugin to support it, though, as connection plugins just need to support the ability to put a file, get a file, and execute a module (assume ftp would also be used rather than netcat?).
To be honest, I considered it as an April fools joke at one point -- to actually implement it -- but I didn't do it.
Most networking equipment -- though a lot of the ways people attempt to configure networking equipment with Ansible can be hacky -- can usually be coerced into enabling SSH.
We would likely refuse the pull request, to be honest -- it is just asking for a world of hurt should MITM possibilities arise.
--Michael