doc: remove private email support address

doc: remove private email support address

Email was never private, and won't further burden myself or
any future maintainers with trying to maintain someone elses'
privacy.

Offering private support is also unfair to readers on public
lists who may get a watered down or improperly translated
summary (if at all).

Instead, encourage the use of anonymity tools and scrubbing of
sensitive information when the sender deems necessary.