[REM] packaging: remove obsolete dependency feedparser

- Up to odoo 10.0, feedparser dependency was optionally used in the cli of vendored html2text.py
  (see https://github.com/odoo/odoo/blob/10.0/addons/mail/models/html2text.py#L437)
- Since 11.0 (67c17cb3), vendored html2text.py has been removed in favor of maintained package
- Turns out the feedparser part in html2text was dead code for a long time anyway
  (see https://github.com/Alir3z4/html2text/issues/220

)
- So we can safely drop this dependency

closes odoo/odoo#76135

Signed-off-by: Christophe Monniez (moc) <moc@odoo.com>