updating readme with py3.10 coming soon

Author: YunchuWang

README.md

@@ -15,7 +15,7 @@ What are the supported Python versions?
 |----------------------------------|------------|------------|------------|------------|-------------|
 | Azure Functions 2.0 (deprecated) | ✔          | ✔          | -          | -          | -           |
 | Azure Functions 3.0              | ✔          | ✔          | ✔          | ✔          | -           |
-| Azure Functions 4.0              | -          | ✔          | ✔          | ✔          | preview     |
+| Azure Functions 4.0              | -          | ✔          | ✔          | ✔          | coming soon     |
 
 For information about Azure Functions Runtime, please refer to [Azure Functions runtime versions overview](https://docs.microsoft.com/en-us/azure/azure-functions/functions-versions) page.