docs(council): Amend Charter for Community Initiative Leads
This commit amends the Fedora Council Charter in the following ways:
* Responsibilities: Add note about Executive Sponsor role and that a
Fedora Council member is expected to become a Sponsor as a part of
their term on the Council.
* Community Initiative Leads: Clarify the role amid recent changes to
Community Initiatives, especially around the composition of the seat
and the fact that Initiatives are not hand-appointed by the Council,
but actually driven by community consensus and momentum.
Closes Fedora-Council/tickets#412.
ref: https://pagure.io/Fedora-Council/tickets/issue/412
Signed-off-by: Justin W. Flory (he/him) <jwf@redhat.com>