[sociald] Increase limit of images fetched per API query.  Contributes to JB#7617
[sociald] Increase limit of images fetched per API query.  Contributes to JB#7617

Previously, the default limit was used for image retrieval queries,
which results in a very large number of API requests being performed
during image sync.  This commit increases the limit to 2000 which
both increases performance (due to round-trip latency) and reduces
the amount of network data and FB API requests being used during sync.

Contributes to JB#7617

rainisto/buteo-sync-plugins-social,rainisto/buteo-sync-plugins-social