Added the gradle plugin SNAPSHOT version support for some tests.

`ImportAndCheckNavigation` and `GradleMultiplatformHighlightingTest` now
use the SNAPSHOT version of the gradle plugin also.

idea/testData/gradle/newMultiplatformHighlighting/first/build.gradle

@@ -1,9 +1,8 @@
 plugins {
-    id 'kotlin-multiplatform' version '1.3.0'
+    id 'org.jetbrains.kotlin.multiplatform' version '{{kotlin_plugin_version}}'
 }
 repositories {
-    mavenCentral()
-    jcenter()
+    {{kotlin_plugin_repositories}}
 }
 kotlin {
     targets {

idea/testData/gradle/newMultiplatformHighlighting/first/settings.gradle

@@ -1,18 +1,6 @@
 pluginManagement {
-    resolutionStrategy {
-        eachPlugin {
-            if (requested.id.id == "kotlin-multiplatform") {
-                useModule("org.jetbrains.kotlin:kotlin-gradle-plugin:${requested.version}")
-            }
-        }
-    }
-
     repositories {
-        mavenCentral()
-
-        maven { url 'https://plugins.gradle.org/m2/' }
-
-        jcenter()
+        {{kotlin_plugin_repositories}}
     }
 }
 rootProject.name = 'first'