fixed slack icon

dashboard/src/shared/common.tsx

@@ -25,7 +25,7 @@ export const integrationList: any = {
     buttonText: "Link a Github Account",
   },
   slack: {
-    icon: "https://image.flaticon.com/icons/png/512/2111/2111615.png",
+    icon: "https://user-images.githubusercontent.com/5147537/54070671-0a173780-4263-11e9-8946-09ac0e37d8c6.png",
     label: "Slack",
     buttonText: "Install Application",
   },