Bump bootstrap from 4.2.1 to 4.3.1

Bumps [bootstrap](https://github.com/twbs/bootstrap) from 4.2.1 to 4.3.1.
- [Release notes](https://github.com/twbs/bootstrap/releases)
- [Commits](https://github.com/twbs/bootstrap/compare/v4.2.1...v4.3.1)

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

package.json

@@ -11,7 +11,7 @@
   },
   "dependencies": {
     "axios": "^0.18.0",
-    "bootstrap": "^4.2.1",
+    "bootstrap": "^4.3.1",
     "bootstrap-vue": "^2.0.0-rc.11",
     "mapbox-gl": "^0.53.0",
     "mapbox-gl-vue": "^1.9.0",