remove code for setting osm2pgsql via config.lib_dir

With the internal osm2pgsql gone, configuration of the binary location
via settings is the only option left that makes sense.

test/python/cli/conftest.py

@@ -69,8 +69,7 @@ def cli_call():
         Returns a function that can be called with the desired CLI arguments.
     """
     def _call_nominatim(*args):
-        return nominatim_db.cli.nominatim(osm2pgsql_path='OSM2PGSQL NOT AVAILABLE',
-                                          cli_args=args)
+        return nominatim_db.cli.nominatim(cli_args=args)
 
     return _call_nominatim