Meilisearch logging is excessively verbose

[ormsbee]

Indexing the Demo course produced ~300 KB of output on a single line of logging:

indexing-output.txt

[bradenmacdonald]

This is the line, and we should simplify it to just state the number of documents rather than logging the actual contents :p

edx-search/search/meilisearch.py

Lines 156 to 161 in dd409f2

	logger.info(
	"Index request: index=%s sources=%s kwargs=%s",
	self.meilisearch_index_name,
	sources,
	kwargs,
	)

Apparently this code hasn't changed in 2 years so I'm surprised nobody else flagged it.