[Clean Up] remove unused vars

[komer3]

ctx input var was not being used by the nodeGetVolumeStats() so removed the unused var

General:

• [ ] Have you removed all sensitive information, including but not limited to access keys and passwords?
• [ ] Have you checked to ensure there aren't other open or closed Pull Requests for the same bug/feature/question?

Pull Request Guidelines:

1. [ ] Does your submission pass tests?
2. [ ] Have you added tests?
3. [ ] Are you addressing a single feature in this PR?
4. [ ] Are your commits atomic, addressing one change per commit?
5. [ ] Are you following the conventions of the language?
6. [ ] Have you saved your large formatting changes for a different PR, so we can focus on your work?
7. [ ] Have you explained your rationale for why this feature is needed?
8. [ ] Have you linked your PR to an open issue

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 37.16%. Comparing base (df301e5) to head (9f45977).

Files	Patch %	Lines
internal/driver/nodeserver.go	0.00%	1 Missing :warning:
internal/driver/nodeserver_all.go	0.00%	1 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #194 +/- ## ======================================= Coverage 37.16% 37.16% ======================================= Files 22 22 Lines 1547 1547 ======================================= Hits 575 575 Misses 938 938 Partials 34 34 ```

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