Section 60. Upon the adoption of Plan B, all heads of departments and members of municipal boards, except the school committee, officials appointed by the governor, and assessors if elected by the people, as their terms of office expire, shall be appointed by the mayor, subject to confirmation by the city council; but the city solicitor shall be appointed, and may be removed, by the mayor, without confirmation by the city council. This section shall apply to the city solicitor in office when Plan B becomes operative.