math/saga: Update to 9.3.0

Again, besides new features, improvements and fixes, the most important
changes are in the PySAGA Python package.

For a list of backward incompatible changes have a look at
https://sourceforge.net/p/saga-gis/code/ci/master/tree/saga-gis/changes.md

Changelog: https://sourceforge.net/p/saga-gis/wiki/Changelog%209.3.0/attachment/changelog_saga_9.3.0.txt

Reported by: portscout, Repology