Update web-ext to 2.9.2

Author: ghostwords

package.json

@@ -6,7 +6,7 @@
     "eslint": "~4.9.0"
   },
   "devDependencies": {
-    "web-ext": "~2.9.1"
+    "web-ext": "~2.9.2"
   },
   "private": true
 }

release-utils/make-signed-xpi.sh

@@ -4,7 +4,7 @@ set -e
 
 cd "$(dirname "$0")"
 
-LATEST_SDK_VERSION=2.9.1
+LATEST_SDK_VERSION=2.9.2
 WEB_EXT=../node_modules/.bin/web-ext
 
 # Auto-generated XPI name from 'web-ext sign'