Update FlexSearch Dependency

[jasontlouro]

This is a critical upgrade, mostly due to this issue. With the default configuration, if a Ghost post title includes the search query, then only those posts with the search query in the title will be returned, even if other posts have the query in other fields like string_tags.

[gmfmi]

Thank you for the feed back. I will do the upgrade but I want to fully re-test everything first before jumping from a 6.x to a 7.x version.