chore(login): update the login banners (#52564)

Updating login banner to include the React Native webinar and a
Profiling blog.

src/sentry/templates/sentry/partial/alerts.html

@@ -78,9 +78,9 @@
   <div class="alert-banner">
     <div class="alert-message">
       {% if banner_choice == 0 %}
-      Scaling your frontend project? Join us July 12th to learn best practices for scaling your frontend project from the engineering team at Unity. &nbsp<a target="_blank" href="https://sentry.io/resources/best-practices-from-unity/?utm_medium=banner&utm_source=sentry-app&utm_campaign=login-frontend-scaling-webinar&utm_content=login-banner&utm_term=">Learn more</a>.
+      Join us July 26th, at 10am PT to hear tips and best practices from React Native experts, including developers from Meta and Expo. &nbsp<a target="_blank" href="https://sentry.io/resources/ama-debugging-react-native-apps-end-to-end/?utm_medium=banner&utm_source=sentry-app&utm_campaign=login-react-native-july&utm_content=login-banner&utm_term=">Learn more</a>.
       {% elif banner_choice == 1 %}
-      Backend Error Monitoring 101 livestream: Join us on July 11th at 10am PT as we cover backend project set up basics and best practices. &nbsp<a target="_blank" href="https://sentry.io/resources/backend-error-monitoring-101/?utm_medium=banner&utm_source=sentry-app&utm_campaign=login-backend-webinar-101&utm_content=login-banner&utm_term=">Learn more</a>.
+      Learn how Profiling for iOS and Android can help you find the sources of main thread contention. &nbsp<a target="_blank" href="https://blog.sentry.io/detecting-main-thread-issues-in-mobile-applications/?utm_medium=banner&utm_source=sentry-app&utm_campaign=login-main-thread-issues&utm_content=login-banner&utm_term=">Learn more</a>.
       {% endif %}
     </div>
   </div>