Pretty Links Developer Edition WordPress Plugin 3.6.17

* Optimize SQL query for Link Health (Pro)

* Fix error on older PHP versions

* Update readme.txt
* Fix JS error on options page
* Set cookie using secure attribute when accessed via secure connection
* Fix PL Link Inserter jumping to bottom of page on WP 6.1
* Fix Gutenberg deprecation notices

* Fix index replacements

* Fix upgrade to Pro bug