Add separate dialog for recovery method removed

The "New Recovery Method" dialog would show if either the recovery method had
been changed or removed, but the dialog text didn't make much sense for the
removed case.

This adds a separate dialog customized for the removed case.

Fixes https://github.com/vector-im/riot-web/issues/8046.

src/async-components/views/dialogs/keybackup/NewRecoveryMethodDialog.js

@@ -71,19 +71,20 @@ export default class NewRecoveryMethodDialog extends React.PureComponent {
     render() {
         const BaseDialog = sdk.getComponent("views.dialogs.BaseDialog");
         const DialogButtons = sdk.getComponent("views.elements.DialogButtons");
-        const title = <span className="mx_NewRecoveryMethodDialog_title">
+
+        const title = <span className="mx_KeyBackupFailedDialog_title">
             {_t("New Recovery Method")}
         </span>;
 
         return (
-            <BaseDialog className="mx_NewRecoveryMethodDialog"
+            <BaseDialog className="mx_KeyBackupFailedDialog"
                 onFinished={this.props.onFinished}
                 title={title}
             >
                 <div>
                     <p>{_t(
                         "A new recovery passphrase and key for Secure " +
-                        "Messages has been detected.",
+                        "Messages have been detected.",
                     )}</p>
                     <p>{_t(
                         "Setting up Secure Messages on this device " +