The accessor functions just look whether a certain flag is set. As these
functions have a different name then the flags, this is more confusing
then helpful. For example, if you want to know where the NM_GENERATED
flag matters, you had to know to grep for nm_settings_connection_get_nm_generated()
in addition to NM_SETTINGS_CONNECTION_FLAGS_NM_GENERATED.

The accessor function hid that the property was implemented as
a connection flag. For example, it was not immediately obvious
that nm_settings_connection_get_nm_generated() is the same
as having the NM_SETTINGS_CONNECTION_FLAGS_NM_GENERATED flag
set.

Drop them.