Switch flag-icon-css to flag-icons in Angular

[MichelZ]

Is there an existing issue for this?

• I have searched the existing issues

Is your feature request related to a problem? Please describe the problem.

warning @volo/language-management > @abp/flag-icon-css > [email protected]: The project has been renamed to flag-icons

package.json:
"@volo/abp.ng.language-management": "~9.0.2",

Describe the solution you'd like

Make sure there is no warning about flag-icon-css anymore.

Additional context

It seems like this was already done somehow:
#15664

But the warning still persists. Make sure the warning does not show anymore