feat: improve "view source"

display encrypted and decrypted event source on the same dialog
keep only one "View Source" action on event context menu

src/components/views/dialogs/UserSettingsDialog.js

@@ -155,7 +155,7 @@ export default class UserSettingsDialog extends React.Component {
         return (
             <BaseDialog className='mx_UserSettingsDialog' hasCancel={true}
                         onFinished={this.props.onFinished} title={_t("Settings")}>
-                <div className='ms_SettingsDialog_content'>
+                <div className='mx_SettingsDialog_content'>
                     <TabbedView tabs={this._getTabs()} initialTabId={this.props.initialTabId} />
                 </div>
             </BaseDialog>