fix(http-caching-proxy): fix compilation error

Author: raymondfeng

packages/http-caching-proxy/package.json

@@ -32,12 +32,11 @@
     "@loopback/build": "^0.7.0",
     "@loopback/testlab": "^0.11.4",
     "@types/debug": "^0.0.30",
-    "@types/delay": "^2.0.1",
     "@types/node": "^10.1.1",
     "@types/p-event": "^1.3.0",
     "@types/request-promise-native": "^1.0.14",
     "@types/rimraf": "^2.0.2",
-    "delay": "^3.0.0"
+    "delay": "^3.1.0"
   },
   "keywords": [
     "LoopBack",

packages/http-caching-proxy/test/integration/http-caching-proxy.integration.ts

@@ -4,7 +4,7 @@
 // License text available at https://opensource.org/licenses/MIT
 
 import {expect} from '@loopback/testlab';
-import * as delay from 'delay';
+import delay from 'delay';
 import * as http from 'http';
 import {AddressInfo} from 'net';
 import * as pEvent from 'p-event';