Committer's Guide … Git … MFC … Examples: none

The 'Examples' subheading that is currently at
https://docs.freebsd.org/en/articles/committers-guide/#_examples
has no subtext.

Hiding the subheading was considered. Instead, it is deleted.

https://bugs.freebsd.org/264080

PR: 264080
Approved by: imp
Differential Revision: https://reviews.freebsd.org/D39384