Change Riot Bot button text and make it a block element

Fixes https://github.com/vector-im/riot-web/issues/8265

src/components/views/settings/tabs/HelpSettingsTab.js

@@ -140,10 +140,12 @@ export default class HelpSettingsTab extends React.Component {
                                              target='_blank'>{sub}</a>,
                         })
                     }
+                    <div>
                         <AccessibleButton onClick={this._onStartBotChat} kind='primary'>
-                        {_t("Start a chat with Riot Bot")}
+                            {_t("Chat with Riot Bot")}
                         </AccessibleButton>
                     </div>
+                </div>
             );
         }