Update kotlinx.datetime

Author: renovate[bot]

gradle/libs.versions.toml

@@ -3,7 +3,7 @@ dokka = "2.0.0"
 kmpmt = "0.1.1"
 kotlin = "2.2.20"
 kotlinx-coroutines = "1.11.0"
-kotlinx-datetime = "0.8.0"
+kotlinx-datetime = "0.8.0-0.6.x-compat"
 poko = "0.20.0"
 publish = "0.34.0"