x11-toolkits/libXaw3d: Assume maintinership

The plan was to ask x11@ to take maintainership, so I proactively
made x11@ maintainer, committing it without realizing that I had not
restored MAINTAINER back to me. This was premature. The PR was opened
to formalize the switch.

PR: 285968
Fixes: d32c335a148f
Approved by: x11@ (manu@)
MFH: 2025Q2