Drop K/N dependency to JCenter

kotlin-native/tools/kotlin-native-gradle-plugin/build.gradle

@@ -26,7 +26,6 @@ buildscript {
         maven {
             url = 'https://cache-redirector.jetbrains.com/jcenter'
         }
-        jcenter()
         maven {
             url "https://cache-redirector.jetbrains.com/plugins.gradle.org/m2/"
         }

kotlin-native/tools/kotlin-native-gradle-plugin/src/test/groovy/org/jetbrains/kotlin/gradle/plugin/test/MultiplatformSpecification.groovy

@@ -34,7 +34,6 @@ class MultiplatformSpecification extends BaseKonanSpecification {
                 maven {
                    url = 'https://cache-redirector.jetbrains.com/jcenter'
                 }
-                jcenter()
             }
             dependencies {
                 classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$KOTLIN_VERSION"
@@ -50,7 +49,6 @@ class MultiplatformSpecification extends BaseKonanSpecification {
             maven {
                url = 'https://cache-redirector.jetbrains.com/jcenter'
             }
-            jcenter()
         }
 
         dependencies {