Bump version for ATN re-upload.

manifest.json

@@ -2,7 +2,7 @@
     "manifest_version": 2,
     "name": "Un-Safelinks",
     "description": "Replace URLs which have been rewritten by Office 365 Advanced Threat Protection with the original URL.",
-    "version": "1.3",
+    "version": "1.3.1",
     "author": "Anton Sarukhanov",
     "homepage_url": "https://github.com/antsar/unsafelinks",
     "applications": {