revert: no need to create a custom writeFile function

Author: codezninja

src/Jenkinsfile.groovy

@@ -124,6 +124,12 @@ class Jenkinsfile implements Resettable {
         return null
     }
 
+    public static String writeFile(String filename, String content) {
+        original.writeFile(file: filename, text: content)
+
+        return null
+    }
+
     public static withInstance(Jenkinsfile newInstance) {
         this.instance = newInstance
     }