Clears any currently stored token. The next time trackdown needs a token, the
token acquisition process starts over, with a fresh call to
trackdown_auth() and, therefore, internally, a call to
gargle::token_fetch(). Unlike some other packages that use gargle,
trackdown is not usable in a de-authorized state. Therefore, calling
trackdown_deauth() only clears the token, i.e. it does NOT imply that
subsequent requests are made with an API key in lieu of a token.
See also
Other auth functions: 
trackdown_auth_configure(),
trackdown_auth()
Examples
if (FALSE) {
trackdown_deauth()
trackdown_user()
}
