Fix dropdown width not adjusting to content

[jpmallarino]

The filter dropdown's width was fixed, preventing it from adjusting to wider content like long collection names. This change allows the dropdown container to resize based on its content. Fixes #13616.

[gasman]

@jpmallarino I notice you've made this change on the stable/7.0.x branch - all pull requests should be made against main. (We will take care of back-porting fixes to stable releases as appropriate.)