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](twbs/bootstrap@v4.2.1...v4.3.1)

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

Author: dependabot[bot]

package-lock.json

@@ -8,7 +8,7 @@
     "lint": "vue-cli-service lint"
   },
   "dependencies": {
-    "bootstrap": "^4.2.1",
+    "bootstrap": "^4.3.1",
     "bootstrap-vue": "^2.0.0-rc.11",
     "buttercms": "^1.2.1",
     "jquery": "^3.3.1",