doc: update note on indexed repositories on sourcegraph.com (!7332) · Merge requests · Administrator / sourcegraph · GitLab

Administrator requested to merge rvt/search-doc-clarify into master Dec 20, 2019

Created by: rvantonder

10K is more accurate based on https://sourcegraph.slack.com/archives/C0W2E592M/p1574452433223800?thread_ts=1574451809.220400&cid=C0W2E592M