fix: upgrade multiple dependencies with Snyk

Snyk has created this PR to upgrade:
  - amphtml-validator from 1.0.30 to 1.0.38.
    See this package in npm: https://www.npmjs.com/package/amphtml-validator
  - through2 from 3.0.1 to 3.0.2.
    See this package in npm: https://www.npmjs.com/package/through2

See this project in Snyk:
https://app.snyk.io/org/mohammed766/project/72a88c73-d142-4f0d-b992-f081d048ea56?utm_source=github&utm_medium=referral&page=upgrade-pr

validator/js/gulpjs/package.json

@@ -17,8 +17,8 @@
     "url": "https://github.com/ampproject/amphtml/tree/master/validator/js/gulpjs"
   },
   "dependencies": {
-    "amphtml-validator": "1.0.30",
-    "through2": "3.0.1"
+    "amphtml-validator": "1.0.38",
+    "through2": "3.0.2"
   },
   "devDependencies": {
     "gulp": "4.0.2",