Removing the properties suggestions feature

This feature is moved directly into Philomena. This implementation is
now outdated and depends on the previous version of suggestions popup.

manifest.json

@@ -33,17 +33,6 @@
                 "src/styles/content/listing.scss"
             ]
         },
-        {
-            "matches": [
-                "*://*.furbooru.org/*"
-            ],
-            "js": [
-                "src/content/header.ts"
-            ],
-            "css": [
-                "src/styles/content/header.scss"
-            ]
-        },
         {
             "matches": [
                 "*://*.furbooru.org/images/*"