fix plugin-id (#59)

Author: martinbonnin

librarian-gradle-plugin/src/main/kotlin/com/gradleup/librarian/gradle/LibrarianPlugin.kt

@@ -6,5 +6,5 @@ import org.gradle.api.Project
 /**
  * Unused plugin, only serves as a convenience to pull the librarian jar into the build classpath
  */
-@GPlugin(id = "com.gradleup.gratatouille")
+@GPlugin(id = "com.gradleup.librarian")
 fun plugin(project: Project) {}