pxgsettings: Fix memory leak of key names
pxgsettings: Fix memory leak of key names

The key names returned by g_settings_list_keys() are annotated as being
transfer full, so must be freed after use.

libproxy/libproxy,horar/libproxy,horar/libproxy,libproxy/libproxy,horar/libproxy,libproxy/libproxy,libproxy/libproxy,horar/libproxy,horar/libproxy,libproxy/libproxy,libproxy/libproxy,libproxy/libproxy,horar/libproxy,horar/libproxy