LI-PS-PDU: rework locationContext drafting note

        -- Drafting note:

        -- Normative text to consider for the standard (e.g., in clause 4.5).

        -- If context[6] is provided, all other provided fields in this instance

        -- of Location shall refer to the same location event.

        -- Otherwise, the absence of context[6] makes no guarantees that this

        -- instance of Location is explicitly for a single location event,

        -- If locationContext[6] is provided, all other provided fields in this

        -- instance of Location shall refer to the same location event.

        -- Otherwise, the absence of locationContext[6] means that there is no

        -- guarantee that this instance of Location is for a single location event,

        -- for backwards compatibility with older interpretations.

        --

    locationContext                 [6] LocationContext OPTIONAL