Spring Upgrade to Kotlin 1.5.21

Comment From: sdeleuze

Reopened due to 66848cfd59ae64d7e93ae35de8c5d946d74ddfac.

Comment From: sdeleuze

Waiting Kotlin 1.5.21 to be released with a fix for https://youtrack.jetbrains.com/issue/KT-47444 to upgrade.