[Security] Bump bootstrap from 3.4.1 to 4.1.2

Bumps [bootstrap](https://github.com/twbs/bootstrap) from 3.4.1 to 4.1.2. **This update includes security fixes.**
- [Release notes](https://github.com/twbs/bootstrap/releases)
- [Commits](twbs/bootstrap@v3.4.1...v4.1.2)

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

package.json

@@ -18,7 +18,7 @@
     "backbone": "^0.9.2",
     "backbone-forms": "^0.14.1",
     "blueimp-file-upload": "^9.31.0",
-    "bootstrap": "^3.4.1",
+    "bootstrap": "^4.1.2",
     "bootstrap-3-typeahead": "^4.0.2",
     "clean-webpack-plugin": "^1.0.1",
     "clipboard": "^2.0.4",