fix(MS Teams): update installation instructions (#14708)

updated installation instructions to match new MS Teams UI

see changes in deploy preview
[here](https://sentry-docs-4jrxqxzll.sentry.dev/organization/integrations/notification-incidents/msteams/)

fixes
https://linear.app/getsentry/issue/RTC-764/update-docs-new-teams-integration-flow-doesnt-send-me-a-channel-pop-up

Author: ameliahsu

docs/organization/integrations/notification-incidents/msteams/img/msteams-open-app.png

@@ -18,16 +18,19 @@ Sentry owner, manager, or admin permissions are required to install this integra
 
 1. Visit [the Microsoft Teams App Store](https://teams.microsoft.com/l/app/5adee720-30de-4006-a342-d454317db1d4)
 
-2. Click the arrow to the right of "Add" to bring up the "Add to Team" button and pick the Team you want for the integration.
+2. Click "Open".
 
-   ![Microsoft Teams installation modal](./img/msteams-add-to-team.png)
+   ![Microsoft Teams installation modal](./img/msteams-open-app.png)
+
+3. Pick the channel where you want to set up Sentry. Click "Go".
+
+   ![Microsoft Teams installation modal with channel selection](./img/msteams-select-channel.png)
 
 <Alert level="warning" title="Note">
-  If you click "Add" instead of "Add to Team", you won't get the welcome message
-  to finish installation.
+  If you click "Open" instead of selecting a channel, this will incorrectly install Sentry as a personal app.
 </Alert>
 
-3. You should see a welcome message in the "General" channel within a few seconds. The welcome message will always appear in the "General" channel, even if you intend to use the integration in another channel. Click "Complete Setup".
+3. You should see a welcome message in your selected channel within a few seconds. Click "Complete Setup".
 
    ![Welcome to Microsoft Teams message](./img/msteams-welcome-message.png)