package/postgis: bump version to 3.1.4

Release-notes: https://git.osgeo.org/gitea/postgis/postgis/raw/tag/3.1.4/NEWS



Signed-off-by: Maxim Kochetkov <fido_max@inbox.ru>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>