Site Health: Move the warning about `WP_DEBUG_LOG` being publicly accessible...

Site Health: Move the warning about `WP_DEBUG_LOG` being publicly accessible from "critical issues" to "recommended improvements" if the error log is outside of the WordPress directory.

Props afragen, Clorith, miss_jwo, mikeschroder, kubiq, xkon.
Fixes #47985.
Built from https://develop.svn.wordpress.org/trunk@47235


git-svn-id: https://core.svn.wordpress.org/trunk@47035 1a063a9b-81f0-0310-95a4-ce76da25c4cd