Remove bind_* params on /register as per MSC2140
Remove bind_* params on /register as per MSC2140

See https://github.com/matrix-org/matrix-doc/pull/2140
See https://github.com/matrix-org/matrix-doc/issues/2253
matrix-org/matrix-doc,matrix-org/matrix-doc,matrix-org/matrix-doc,matrix-org/matrix-doc