Replace khttp

With this MR, we replace khttp with the built-in Java HTTP client. This means, we also do no longer depend on the jcenter repository.

Fix #287 (closed).

theodolite/src/main/kotlin/rocks/theodolite/kubernetes/operator/ClusterSetup.kt

@@ -80,7 +80,7 @@ class ClusterSetup(
             labelValue = "theodolite"
         )
         try {
-            resourceRemover.removeCR(
+            resourceRemover.removeGenericResources(
                 labelName = "app.kubernetes.io/created-by",
                 labelValue = "theodolite",
                 context = serviceMonitorContext