Update plugin dokka to v1.9.20 (#306)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

gradle/libs.versions.toml

@@ -9,5 +9,5 @@ coroutines-test = { module = "org.jetbrains.kotlinx:kotlinx-coroutines-test", ve
 kotlin = { id = "org.jetbrains.kotlin.multiplatform", version = "1.9.22" }
 spotless = { id = "com.diffplug.spotless", version = "6.25.0" }
 publish = { id = "com.vanniktech.maven.publish", version = "0.27.0" }
-dokka = { id = "org.jetbrains.dokka", version = "1.9.10" }
+dokka = { id = "org.jetbrains.dokka", version = "1.9.20" }
 kotlinApiDump = { id = "org.jetbrains.kotlinx.binary-compatibility-validator", version = "0.14.0" }