Update marketing doc site version

Author: mc-keith

spec/marketing.json

@@ -800,7 +800,7 @@
     },
     "swagger": "2.0",
     "info": {
-        "version": "3.0.77",
+        "version": "3.0.78",
         "title": "Mailchimp Marketing API",
         "contact": {
             "name": "Mailchimp API Support",