advocacy/myths.adoc: correct title and subheading

[grahamperrin]

Summary

The title of https://www.freebsd.org/advocacy/myths/ is identical to https://www.freebsd.org/advocacy/. Different pages should not share a single title.

Correct the title, and rationalise a subheading.

Test Plan

Preview in GitHub: https://github.com/grahamperrin/freebsd-doc/blob/advocacy-myths/website/content/en/advocacy/myths.adoc.

[carlavilla]

Nice improvement :)

[gjb]

Approved.

[grahamperrin]

5e11de6140fc1ef5a6e40523b9e74ca44cc0d48a

• https://cgit.freebsd.org/doc/commit/?id=5e11de6140fc1ef5a6e40523b9e74ca44cc0d48a
  • affected by FreeBSD bug 266473 – cgit.freebsd.org breaks some links – seems to not recognise some types of URI delimiter (RFC 3986)
• https://codeberg.org/FreeBSD/freebsd-doc/commit/5e11de6140fc1ef5a6e40523b9e74ca44cc0d48a
• https://github.com/freebsd/freebsd-doc/commit/5e11de6140fc1ef5a6e40523b9e74ca44cc0d48a
• https://gitlab.com/FreeBSD/freebsd-doc/-/commit/5e11de6140fc1ef5a6e40523b9e74ca44cc0d48a

GitHub, wiki, www.freebsd.org

Branch advocacy-myths remains in my fork, for https://github.com/grahamperrin/freebsd-doc/blob/advocacy-myths/website/content/en/advocacy/myths.adoc.

There's more to do at https://wiki.freebsd.org/Myths (discussion in #freebsd-wiki in IRC) parallel to FreeBSD Myths and Realities | The FreeBSD Project …