Update to the Process for Selection of Trustees for the IETF Trust

This memo updates the process for selection of Trustees for the IETF Trust. Previously, the IETF Administrative Oversight Committee (IAOC) members also acted as Trustees, but the IAOC has been eliminated as part of an update to the structure of the IETF Administrative Support Activity (IASA). This memo specifies that the Trustees shall be selected separately. This memo obsoletes RFC 4371. The changes relate only to the selection of Trustees. All other aspects of the IETF Trust remain as they are today.