Bump react-bootstrap from 1.6.1 to 1.6.4 in /example

Bumps [react-bootstrap](https://github.com/react-bootstrap/react-bootstrap) from 1.6.1 to 1.6.4.
- [Release notes](https://github.com/react-bootstrap/react-bootstrap/releases)
- [Changelog](https://github.com/react-bootstrap/react-bootstrap/blob/v1.6.4/CHANGELOG.md)
- [Commits](react-bootstrap/react-bootstrap@v1.6.1...v1.6.4)

---
updated-dependencies:
- dependency-name: react-bootstrap
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

example/package-lock.json

@@ -20,7 +20,7 @@
     "@rjsf/core": "^2.4.1",
     "bootstrap": "^4.6.0",
     "react": "file:../node_modules/react",
-    "react-bootstrap": "^1.4.2",
+    "react-bootstrap": "^1.6.4",
     "react-dom": "file:../node_modules/react-dom",
     "react-json-editor-ajrm": "^2.5.13"
   },