databases/grass7: add SONAME and use new path for graphics/qgis*
- Add SONAME (upstreamed) [1]
- Remove the (bad) idea to keep a symlink to the old path logic (grass-M.m.b)
- Fix FindGRASS.cmake for graphics/qgis and graphics/qgis-ltr (upstreamed) [2]
[1] https://github.com/OSGeo/grass/pull/301 [2] https://github.com/qgis/QGIS/pull/34088