group admin form should allow acronyms that start with numbers other sdo groups.

[rjsparks]

We already have things like '3gpp-tsgct', '3gpp-tsgct-ct1', '3gpp-tsgct-ct3', '3gpp-tsgct-ct4'. If we want more 3gpp-tsgct, the admin shouldn't block us.

[rjsparks]

But any IETF, IRTF, IAB, etc related groups should follow the current restrictions