graphics/proj: Update to 6.3.1
* Update to 6.3.1
* Move CONFLICTS_INSTALL (pet portlint)
Changelog:
- https://github.com/OSGeo/PROJ/releases/tag/6.3.1
- https://github.com/OSGeo/PROJ/releases/tag/6.3.0
- https://github.com/OSGeo/PROJ/releases/tag/6.2.1
- https://github.com/OSGeo/PROJ/releases/tag/6.2.0