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>