[python] generated tests should not suggest read-only in request

transferred from https://github.com/Azure/autorest.python/issues/2978

See this field that is `visibility("read")`:
https://github.com/Azure/azure-rest-api-specs/blob/c9a4dc04527f7fdb4a944e2c392f2de280ef7cae/specification/durabletask/DurableTask.Management/main.tsp#L70

And the generated test for Python looks like this:
```
@recorded_by_proxy
def test_schedulers_begin_update(self, resource_group):
response = self.client.schedulers.begin_update(
resource_group_name=resource_group.name,
scheduler_name="str",
properties={
"location": "str",
"id": "str",
"name": "str",
"properties": {
"ipAllowlist": ["str"],
"sku": {"name": "str", "capacity": 0, "redundancyState": "str"},
"endpoint": "str",
"provisioningState": "str",
},
"systemData": {
"createdAt": "2020-02-20 00:00:00",
"createdBy": "str",
"createdByType": "str",
"lastModifiedAt": "2020-02-20 00:00:00",
"lastModifiedBy": "str",
"lastModifiedByType": "str",
},
"tags": {"str": "str"},
"type": "str",
},
).result() # call '.result()' to poll until service return final result
```

Note that we suggest `redundancyState` in the request. As this field is "read", it should not be suggested and should be ommmited.