Fix license

  - On October 18, 2021, Sequoia PGP's license was changed from the
    GPL to the LGPL.  Unfortunately, we forgot to update sq's license.

  - See sequoia@884639bf

  - Change Sequoia's license from GPL 2.0 or later to LGPL 2.0 or
    later as unanimously decided on October 18, 2021 by:

      - Christof Wahl <cw@pep.security> (pEp security CEO)
      - Heiko Schaefer <heiko.schaefer@posteo.de> (pEp Foundation
        employee, Sequoia developer)
      - Justus Winter <justus@sequoia-pgp.org> (pEp Foundation
        employee, Sequoia Founder)
      - Neal H. Walfield <neal@pep.foundation> (pEp Foundation
        employee, Sequoia Founder)
      - Patrick Meier <pm@pep.security> (pEp security Chief Product
        and Service Officer)
      - Rudolf Bohli <rb@pep.security> (pEp security Chairman of the
        Board)
      - Volker Birk <vb@pep.security> (pEp security Founder, pEp
        Foundation Council)