Mixpanel Autotrack Deprecated

Mixpanel reached out to Success Eng to ask us to remove references to Autotrack as it has been disabled. In our doc we have two references, one under features and the other under appendices. I updated the first reference (under features) to advise of this change, and removed the section under Appendices.

Author: segment-sv

src/connections/destinations/catalog/mixpanel/index.md

@@ -311,7 +311,7 @@ We do not map `$library_version` since that is reserved for Mixpanel's library v
 
 ### Autotrack
 
-Mixpanel's [Autotrack](https://mixpanel.com/autotrack/) feature is supported using Segment as long as you are using one of our client-side libraries ([analytics.js](/docs/connections/sources/catalog/libraries/website/javascript/), [iOS](/docs/connections/sources/catalog/libraries/mobile/ios/), [Android](/docs/connections/sources/catalog/libraries/mobile/android/)). Additionally, if you're using analytics for Android or iOS, make sure your Mixpanel destination is bundled - otherwise Autotrack will not work. Once Mixpanel is installed using Segment, all you have to do is [enable the Autotrack feature for your Mixpanel account](https://mixpanel.com/help/questions/articles/what-is-autotrack-and-how-do-i-get-started-using-it) and it will start working.
+Mixpanel has discontinued Autotrack functionality as of February 2021. If you were previously using this functionality, it will no longer be available.
 
 ### People
 
@@ -450,10 +450,6 @@ If you are testing in Xcode remember you must first background the app, then the
 
 ## Appendices
 
-### Autotrack
-
-Mixpanel's [Autotrack](https://mixpanel.com/autotrack/) feature is supported using Segment as long as you are using one of our client-side libraries ([analytics.js](/docs/connections/sources/catalog/libraries/website/javascript/), [iOS](/docs/connections/sources/catalog/libraries/mobile/ios/), [Android](/docs/connections/sources/catalog/libraries/mobile/android/)). Additionally, if you're using analytics for Android or iOS, make sure your Mixpanel destination is bundled - otherwise Autotrack will not work. Once Mixpanel is installed using segment, all you have to do is [enable the Autotrack feature for your Mixpanel account](https://mixpanel.com/help/questions/articles/what-is-autotrack-and-how-do-i-get-started-using-it) and it will start working.
-
 ### IP
 
 If an `ip` property is passed to Mixpanel, the value will be interpreted as the IP address of the request and therefore automatically parsed into Mixpanel geolocation properties (City, Country, Region). After that IP address has been parsed, they will throw out the IP address and only hold onto those resulting geolocation properties. As such, if you want to display an IP address as a property within the Mixpanel UI or within raw data, you will simply want to slightly modify the naming convention for that property.