fix clippy warning

[jimexist]

Which issue does this PR close?

We generally require a GitHub issue to be filed for all bug fixes and enhancements and this helps us generate change logs for our releases. You can link an issue to this PR using the GitHub syntax. For example Closes #123 indicates that this PR will close issue #123.

Closes #.

This PR does not close any issue, because it's mainly a quick fix.

Rationale for this change

Why are you proposing this change? If this is already explained clearly in the issue then this section is not needed.
Explaining clearly why changes are proposed helps reviewers understand your changes and offer better suggestions for fixes.

What changes are included in this PR?

There is no need to duplicate the description in the issue here but it is sometimes worth providing a summary of the individual changes in this PR.

Are there any user-facing changes?

If there are user-facing changes then we may require documentation to be updated before approving the PR.

If there are any breaking changes to public APIs, please add the breaking change label.

[codecov-commenter]

Codecov Report

Merging #286 (77e3b9c) into master (9dface6) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #286   +/-   ##
=======================================
  Coverage   76.19%   76.19%           
=======================================
  Files         140      140           
  Lines       23595    23595           
=======================================
  Hits        17978    17978           
  Misses       5617     5617           

Impacted Files	Coverage Δ
...tafusion/src/physical_plan/distinct_expressions.rs	90.34% <ø> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update 9dface6...77e3b9c. Read the comment docs.

[jorgecarleitao]

Thank you, @jimexist 👍