Clears any currently stored token. The next time bigrquery needs a token, the
token acquisition process starts over, with a fresh call to bq_auth() and,
therefore, internally, a call to gargle::token_fetch(). Unlike some other
packages that use gargle, bigrquery is not usable in a de-authorized state.
Therefore, calling bq_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:
bq_auth(),
bq_auth_configure()