Bump bootstrap from 4.1.3 to 4.3.1

Bumps [bootstrap](https://github.com/twbs/bootstrap) from 4.1.3 to 4.3.1.
- [Release notes](https://github.com/twbs/bootstrap/releases)
- [Commits](https://github.com/twbs/bootstrap/compare/v4.1.3...v4.3.1)

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

package.json

@@ -29,7 +29,7 @@
     "@angular/router": "^6.1.0",
     "@ng-bootstrap/ng-bootstrap": "^3.3.1",
     "@types/moment-timezone": "^0.5.12",
-    "bootstrap": "^4.1.3",
+    "bootstrap": "^4.3.1",
     "core-js": "^2.5.4",
     "moment-timezone": "^0.5.25",
     "rxjs": "~6.2.0",