Switch back to using published plugin

src/resources/init-scripts/github-dependency-graph-gradle-plugin-apply.groovy

@@ -1,6 +1,9 @@
 buildscript {
+  repositories {
+    gradlePluginPortal()
+  }
   dependencies {
-    classpath files("github-dependency-graph-gradle-plugin-0.0.3.jar")
+    classpath "org.gradle:github-dependency-graph-gradle-plugin:0.0.3"
   }
 }
 apply plugin: org.gradle.github.GitHubDependencyGraphPlugin