Bump codemirror from 5.36.0 to 5.51.0

Bumps [codemirror](https://github.com/codemirror/CodeMirror) from 5.36.0 to 5.51.0.
- [Release notes](https://github.com/codemirror/CodeMirror/releases)
- [Changelog](https://github.com/codemirror/CodeMirror/blob/master/CHANGELOG.md)
- [Commits](https://github.com/codemirror/CodeMirror/compare/5.36.0...5.51.0)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

package.json

@@ -40,7 +40,7 @@
     "babel-preset-react": "^6.24.1",
     "body-parser": "^1.14.2",
     "classnames": "^2.2.6",
-    "codemirror": "^5.22.0",
+    "codemirror": "^5.51.0",
     "cookie-parser": "^1.4.3",
     "create-react-class": "^15.6.3",
     "express": "^4.13.3",