databases/postgis25, databases/postgis30: Update to latest versions

• databases/postgis25
  • • Update to 2.5.4
    • Add an option to NLS
    • Move CONFLICTS_INSTALL (pet portlint)
  • databases/postigs30
    • Update to 3.0.1

Changelog:

• https://postgis.net/2020/02/28/postgis-2.5.4/
• https://postgis.net/2020/02/20/postgis-3.0.1/

Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D24301