Remove setup.css from content script.

BUG=481533

Review URL: https://codereview.chromium.org/1108843003

Cr-Commit-Position: refs/heads/master@{#327086}

ui/accessibility/extensions/colorenhancer/manifest.json

 {
   "name": "__MSG_COLOR_ENHANCER_APPNAME__",
-  "version": "1.12.2",
+  "version": "1.12.3",
   "description": "__MSG_COLOR_ENHANCER_APPDESC__",
   "manifest_version": 2,
   "icons": {
@@ -35,8 +35,7 @@
         "<all_urls>"
       ],
       "css": [
-        "res/cvd.css",
-        "res/setup.css"
+        "res/cvd.css"
       ],
       "js": [
         "src/common.js",