Update Privacy Policy (#2860)

* Update Privacy Policy

Supersedes #2775

Signed-off-by: Thib <thib@ergaster.org>

* Update content/legal/privacy-notice.md

Co-authored-by: Hugh Nimmo-Smith <hughns@users.noreply.github.com>

* Fix leftover bold titles

Signed-off-by: Thib <thib@ergaster.org>

* Remove ref to matrix archive

Signed-off-by: Thib <thib@ergaster.org>

* Add markup for world_readable

Signed-off-by: Thib <thib@ergaster.org>

* Fix remainign remarks

Signed-off-by: Thib <thib@ergaster.org>

* Drop Hydrogen

Signed-off-by: Thib <thib@ergaster.org>

* Fix remaining nits

Signed-off-by: Thib <thib@ergaster.org>

* Use a relative link when linking to m.org

Signed-off-by: Thib <thib@ergaster.org>

* Fix headings

Signed-off-by: Thib <thib@ergaster.org>

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Signed-off-by: Thib <thib@ergaster.org>
Co-authored-by: Hugh Nimmo-Smith <hughns@users.noreply.github.com>

Author: thibaultamartin