Update kotlin monorepo to v2.2.20-RC (#2565)

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

gradle/libs.versions.toml

@@ -19,7 +19,7 @@ compose-bom = "2025.08.00"
 compose-multiplatform = "1.8.2"
 compose-destinations = "2.2.0"
 compose-preference = "2.1.0"
-kotlin = "2.2.20-Beta2"
+kotlin = "2.2.20-RC"
 kotlinx-coroutines = "1.10.2"
 kotlinx-datetime = "0.7.1"
 kotlinx-serialization = "1.9.0"