Upgrade to Dokka 1.7.20

See gh-29308

Author: izeye

build.gradle

@@ -1,7 +1,7 @@
 plugins {
 	id 'io.spring.nohttp' version '0.0.10'
 	id 'io.freefair.aspectj' version '6.5.0.3' apply false
-	id 'org.jetbrains.dokka' version '1.7.10' apply false
+	id 'org.jetbrains.dokka' version '1.7.20' apply false
 	id 'org.jetbrains.kotlin.jvm' version '1.7.20' apply false
 	id 'org.jetbrains.kotlin.plugin.serialization' version '1.7.20' apply false
 	id 'org.asciidoctor.jvm.convert' version '3.3.2'