Remove Bintray ktor usage from kotlin-native

(cherry picked from commit 8a5987d82191da66b31ef10363cebc1a784e31b3)

kotlin-native/build-tools/src/main/kotlin/org/jetbrains/kotlin/CopySamples.kt

@@ -59,7 +59,6 @@ open class CopySamples : Copy() {
 
     private val replacements = listOf(
         "https://dl.bintray.com/kotlin/kotlin-eap" to "https://cache-redirector.jetbrains.com/dl.bintray.com/kotlin/kotlin-eap",
-        "https://dl.bintray.com/kotlin/ktor" to "https://cache-redirector.jetbrains.com/dl.bintray.com/kotlin/ktor",
         "https://plugins.gradle.org/m2" to "https://cache-redirector.jetbrains.com/plugins.gradle.org/m2",
         "mavenCentral()" to "maven { setUrl(\"https://cache-redirector.jetbrains.com/maven-central\") }",
         "jcenter()" to "maven { setUrl(\"https://cache-redirector.jetbrains.com/jcenter\") }"

kotlin-native/samples/html5Canvas/build.gradle.kts

@@ -8,7 +8,7 @@ plugins {
 
 repositories {
     jcenter()
-    maven("https://dl.bintray.com/kotlin/ktor")
+    mavenCentral()
 }
 
 val hostOs = System.getProperty("os.name")