x11/xorgproto: Update to 2021.5

There's no changelog by upstream, commit log:
https://gitlab.freedesktop.org/xorg/proto/xorgproto/-/commits/master

Exp-run by: antoine
PR: 259600
Approved by: arrowd (mentor), zeising (member of x11@)
Differential Revision: https://reviews.freebsd.org/D32766