Add notice for version 1 deprecation (#21680)

* Add notice for version 1 deprecation

* Update README.md

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Co-authored-by: Chenjie Shi <tadelesh.shi@live.cn>

README.md

@@ -16,6 +16,8 @@ To get started with a module, see the README.md file located in the module's pro
 
 > NOTE: Go **1.18** or later is required. You could download and install the latest version of Go from [here](https://go.dev/doc/install). It will replace the existing Go on your machine. If you want to install multiple Go versions on the same machine, you could refer this [doc](https://go.dev/doc/manage-install).
 
+> NOTE: The [root azure-sdk-for-go Go module](https://godoc.org/github.com/Azure/azure-sdk-for-go) which contains subpaths of `/services/**/mgmt/**` (also known as track 1) is [deprecated and no longer recieving support](https://azure.github.io/azure-sdk/releases/deprecated/go.html). See [the migration guide](https://github.com/Azure/azure-sdk-for-go/blob/main/documentation/MIGRATION_GUIDE.md) to learn how to migrate to the current version.
+
 ## Packages available
 
 Each service can have both 'client' and 'management' modules. 'Client' modules are used to consume the service, whereas 'management' modules are used to configure and manage the service.