Bump to latest react-gemini-scrollbar

I've updated our forks of the gemini-scrollbar project to latest upstream.

package.json

@@ -39,7 +39,7 @@
     "extract-text-webpack-plugin": "^0.9.1",
     "filesize": "^3.1.2",
     "flux": "~2.0.3",
-    "gemini-scrollbar": "matrix-org/gemini-scrollbar#87ebaa7",
+    "gemini-scrollbar": "matrix-org/gemini-scrollbar#468544d",
     "gfm.css": "^1.1.1",
     "highlight.js": "^9.0.0",
     "linkifyjs": "^2.0.0-beta.4",
@@ -51,7 +51,7 @@
     "react-dnd": "^2.1.4",
     "react-dnd-html5-backend": "^2.1.2",
     "react-dom": "^15.0.1",
-    "react-gemini-scrollbar": "matrix-org/react-gemini-scrollbar#c3d942e",
+    "react-gemini-scrollbar": "matrix-org/react-gemini-scrollbar#dbf0abf",
     "sanitize-html": "^1.11.1"
   },
   "devDependencies": {