databases/postgis-jdbc: Fix install data path

Package builders complain about an error in staging:
install -m 0644 /portdistfilespostgis-jdbc-2.1.7.jar /wrkdirs/usr/ports/databases/postgis-jdbc/work/stage/usr/local/share/java/classes
install: /portdistfilespostgis-jdbc-2.1.7.jar: No such file or directory

Don't know, why this worked before for such a long time ...

While here, pet portlint for PLIST_FILES.

Reported by: pkg-fallout
MFH: 2025Q3