fix(apm): Set transaction name on componentDidMount() (#18836)

Author: dashed

src/sentry/static/sentry/app/views/app/index.tsx

@@ -82,6 +82,8 @@ class App extends React.Component<Props, State> {
   }
 
   componentDidMount() {
+    this.updateTracing();
+
     this.props.api.request('/organizations/', {
       query: {
         member: '1',