[MM-51680] : Revert New Browse Channels UI modal changes (https://github.com/mattermost/mattermost-webapp/pull/11262) (#22613)

* Revert https://github.com/mattermost/mattermost-webapp/pull/11262

* fix missing translation

* fix indentation issue

* fix imports in Update accessibility_modals_dialogs_spec.js

---------

Co-authored-by: Mattermost Build <build@mattermost.com>

webapp/platform/components/src/generic_modal/generic_modal.tsx

@@ -38,7 +38,6 @@ export type Props = {
     compassDesign?: boolean;
     backdrop?: boolean;
     backdropClassName?: string;
-    headerButton?: React.ReactNode;
     tabIndex?: number;
     children: React.ReactNode;
     keyboardEscape?: boolean;
@@ -166,7 +165,6 @@ export class GenericModal extends React.PureComponent<Props, State> {
                 <h1 id='genericModalLabel'>
                     {this.props.modalHeaderText}
                 </h1>
-                {this.props.headerButton}
             </div>
         );