Button groups and split buttons example lacks border-radius on right due to incorrect markup order

[shmert]

Bug description:

The example for split buttons has sharp right corners on the "Split Me" button. Moving some tags around fixes this.

Link to minimally-working StackBlitz that reproduces the issue:

https://angular-f1ubcd.stackblitz.io

Versions of Angular, ng-bootstrap and Bootstrap:

Angular: 17.0.8

ng-bootstrap: 16.0.0

Bootstrap: Not sure?

[jnizet]

Good catch.

Would you fancy opening a pull request to fix this?