ABPSC — Remove bar on AB members being TF/SIG Chairs

(This has been discussed and minuted without a formal issue)
The following sentence should be removed "AB
members may not simultaneously chair any OMG Subgroup except an
Architecture Board Subgroup, a Revision Task Force or a Finalisation Task Force."
As well as the note:
"[AB members are expected to participate in many of the parallel Subgroup
meetings during an OMG Technical Meeting week, so it would not in general
be feasible for them also to run Subgroups. However, RTFs & FTFs typically
meet briefly, if at all, during technical meeting weeks, so there is little
possibility of scheduling clashes, whilst preventing AB members running the
Subgroups they themselves charter would be rather contradictory.]"

The explanation given does not reflect current practice, especially given that AB members are no longer assigned as official "AB Buddy" to Subgroups and many Subgroups meet only for a few hours each meeting.