az provider show -n <namespace> doesn't work for most RPs

### **This is autogenerated. Please review and update as needed.**

## Describe the bug
az provider show -n should pull info from the providers api for the specified provider. It looks as though we use an arbitrary apiVersion which isn't likely to match the supported apiVersion for the specified provider. So this cmd will almost never work

**Command Name**
``az provider show

**Errors:**
Error returned will indicate the provider doesn't support the apiVersion sent in the request. The use has no option to change the apiVersion

## To Reproduce:
Steps to reproduce the behavior. Note that argument values have been redacted, as they may contain sensitive information.

az provider show -n Microsoft.Storage/storageAccounts (or any resource that doesn't have a 2020-06-01 apiVersion

- _Put any pre-requisite steps here..._
- ``

## Expected Behavior
return the results of the GET

## Environment Summary
```
Windows-10-10.0.18362-SP0
Python 3.6.8
Installer: MSI

azure-cli 2.14.0 *

Extensions:
storage-preview 0.2.5

```
## Additional Context