Lower default batch size for skipParse

The current default, 500, put too much load on the Elasticsearch servers
when indexing.  If it put too much load for WMF it likely puts too much
load for everyone else that might use it.

Change-Id: I1c9cc76c43b711cc9d47b65490d7488b0c147f1e
Merge "Lower default batch size for skipParse"