bump react-gemini-scrollbar

package.json

@@ -58,7 +58,6 @@
     "favico.js": "^0.3.10",
     "filesize": "^3.1.2",
     "flux": "~2.0.3",
-    "gemini-scrollbar": "matrix-org/gemini-scrollbar#b302279",
     "gfm.css": "^1.1.1",
     "highlight.js": "^9.0.0",
     "linkifyjs": "^2.1.3",
@@ -70,7 +69,7 @@
     "react-dnd": "^2.1.4",
     "react-dnd-html5-backend": "^2.1.2",
     "react-dom": "^15.4.0",
-    "react-gemini-scrollbar": "matrix-org/react-gemini-scrollbar#5e97aef",
+    "react-gemini-scrollbar": "matrix-org/react-gemini-scrollbar#39d858c",
     "sanitize-html": "^1.11.1",
     "ua-parser-js": "^0.7.10",
     "url": "^0.11.0"