[Storage] Pageable operations attempt to deserialize `204 No Content`

More context found in this PR comment: https://github.com/Azure/azure-sdk-for-rust/pull/5273/changes#r3973832539

But in short:
- TypeSpec Rust emitter treats every successful (2xx) response as having a body that needs to be deserialized
- However, 204 literally maps to `No Content`, meaning there is no body
- Therefore, for a 204 it still attempts to deserializes, and since there is no body, it will actually bubble this up as some sort of deserialization error
- I believe the correct behavior here is that `204 No Content` should be explicitly handled to _not_ attempt deserialization

The above PR comment targets a mocked test showing this attempt to deserialize on a 204 response.

Start with the mocked test referenced in the linked pull request comment and trace the generated response handling for a pageable operation returning 204. Confirm that the no-content response completes without deserialization and that the test no longer reports a deserialization error.

Written by the indexing model from the issue text.