Change flux version to 2.1.1

It was previously pinned to 2.0.3 in https://github.com/vector-im/riot-web/commit/5bab440a1
but only here and not in react-sdk, meaning that react-sdk was
still using the latest, at least in develop builds, however
react-sdk now uses utils which requires 2.1, so pin to 2.1.1
everywhere for sanity.

package.json

@@ -60,7 +60,7 @@
     "extract-text-webpack-plugin": "^0.9.1",
     "favico.js": "^0.3.10",
     "filesize": "3.5.6",
-    "flux": "~2.0.3",
+    "flux": "2.1.1",
     "gemini-scrollbar": "matrix-org/gemini-scrollbar#b302279",
     "gfm.css": "^1.1.1",
     "highlight.js": "^9.0.0",