ci(tsc): Fixes build.

src/statementCreators/actionOnSiteActivity.ts

@@ -1,4 +1,4 @@
-import { Moment } from 'moment';
+import { Duration } from 'moment';
 import UserSiteActivityAction from '../actionUtils/UserSiteActivityAction';
 import { site, source } from '../statementConstants/activityTypes';
 import createActivity from '../statementUtils/createActivity';
@@ -18,8 +18,8 @@ export interface SiteActivityAction extends UserSiteActivityAction {
   /** Determines if the activity was passed or failed. */
   readonly passed?: boolean;
 
-  /** Determines how long the activity took as an ISO Duration. */
-  readonly duration?: Moment.Duration;
+  /** Determines how long the activity took. */
+  readonly duration?: Duration;
 }
 
 /**
@@ -45,7 +45,9 @@ export default function actionOnSiteActivity(action: SiteActivityAction): Statem
       result: pickDefined({
         completion: action.completed,
         success: action.passed,
-        duration: action.duration,
+        duration: action.duration === undefined ? undefined : (
+          action.duration.toISOString()
+        ),
       }),
     }),
     context: {