Add mock for the unlink dropbox endpoint

GitOrigin-RevId: 41293a2cb6ab3cf87d40717e43c0f4888df89fe1

services/web/test/acceptance/src/mocks/MockThirdPartyDataStoreApi.js

@@ -7,8 +7,15 @@ class MockThirdPartyDataStoreApi extends AbstractMockApi {
     res.sendStatus(200)
   }
 
+  unlinkUser(req, res) {
+    res.sendStatus(200)
+  }
+
   applyRoutes() {
     this.app.delete('/user/:user_id', (req, res) => this.deleteUser(req, res))
+    this.app.delete('/user/:user_id/dropbox', (req, res) =>
+      this.unlinkUser(req, res)
+    )
   }
 }