Man page references non-existing oauth example

[particleflux]

The imap_config manpage references an alleged example for oauth2 authentication in the samples/extend.lua file.

Yet there is no such example in there.

https://github.com/lefcha/imapfilter/blob/72f7fa621357299bb6c8f5d29b4efbafcbd34bf7/doc/imapfilter_config.5#L289C1-L291C57