[ML13] Fix the locale passing in ProximityInfo

The locale is used to determine additional proximity characters. This
is dependent on the dictionary language, but was passed as a function
of the layout, which is wrong and would have given bad suggestions in
multi-lingual mode.

Ideally, additional proximity characters should be inserted in the
dictionary header, but for now it's a rather simple change to get
it from the dictionary's locale instead of the proximity info locale.

Also, that allows us to remove completely the locale parameter from
proximity info, which is a much needed change.

This change has zero effect on unit tests and on regression tests.

Bug: 11230254
Change-Id: If95157155db7dccd1f00b8ba55ccb3600283f9e4