enterprise home: use larger page size when requesting searches in repo panel

Created by: attfarhan

Addresses one bug in https://github.com/sourcegraph/sourcegraph/issues/13835. Sometimes the repo panel may not be populated fully because not every search has a repo filter, and we fetched only 20 recent searches at a time. Increasing the number of searches we fetch gives us better odds of filling up the panel with repo filter values.