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

PR: 243558
Approved by: wen (maintainer), tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D23619