Bump gemini-scrollbar to latest version

RoomDirectory uses react-gemini-scrollbar directly, so make sure we are using a
consistent version.

package.json

@@ -33,7 +33,7 @@
     "extract-text-webpack-plugin": "^0.9.1",
     "filesize": "^3.1.2",
     "flux": "~2.0.3",
-    "gemini-scrollbar": "matrix-org/gemini-scrollbar#75aecd7",
+    "gemini-scrollbar": "matrix-org/gemini-scrollbar#7dc736d",
     "gfm.css": "^1.1.1",
     "highlight.js": "^9.0.0",
     "linkifyjs": "^2.0.0-beta.4",
@@ -45,7 +45,7 @@
     "react-dnd": "^2.0.2",
     "react-dnd-html5-backend": "^2.0.0",
     "react-dom": "^0.14.2",
-    "react-gemini-scrollbar": "^2.0.1",
+    "react-gemini-scrollbar": "matrix-org/react-gemini-scrollbar#869a86b",
     "sanitize-html": "^1.11.1"
   },
   "devDependencies": {