Xaw3d: 1.6.2 -> 1.6.3 (#42417)

Semi-automatic update generated by https://github.com/ryantm/nixpkgs-update tools.

This update was made based on information from https://repology.org/metapackage/Xaw3d/versions.

These checks were done:

- built on NixOS

- 0 of 0 passed binary check by having a zero exit code.
- 0 of 0 passed binary check by having the new version present in output.
- found 1.6.3 with grep in /nix/store/p7q0v9qpcijqpb6qq0zpw1aqxfxirb4n-Xaw3d-1.6.3
- directory tree listing: https://gist.github.com/27b4fc05ea0d4751eb7c7dadc48953a9
- du listing: https://gist.github.com/1eaddadb1913f4473d1335eaa0d7fc4d