chore(deps): update dependency mobx to v5

Author: renovate-bot

package.json

@@ -74,7 +74,7 @@
         "html-webpack-plugin": "3.2.0",
         "jest": "22.4.4",
         "jest-enzyme": "6.0.0",
-        "mobx": "4.3.0",
+        "mobx": "5.7.0",
         "mobx-react": "5.1.2",
         "react": "16.4.0",
         "react-dom": "16.4.0",

yarn.lock

@@ -5844,9 +5844,9 @@ mobx-react@5.1.2:
     hoist-non-react-statics "^2.5.0"
     react-lifecycles-compat "^3.0.2"
 
-mobx@4.3.0:
-  version "4.3.0"
-  resolved "https://registry.yarnpkg.com/mobx/-/mobx-4.3.0.tgz#50a5e63fd0197a83c68166ff83ada45b65c859f8"
+mobx@5.7.0:
+  version "5.7.0"
+  resolved "https://registry.yarnpkg.com/mobx/-/mobx-5.7.0.tgz#dc58cd02fbacc5346071c3e6563b6507aff71f59"
 
 move-concurrently@^1.0.1:
   version "1.0.1"