chore: make cargo clippy happy in nigtly

[xudong963]

Make Cargo Clippy happy in nightly mode, making code more elegant

[Dandandan]

Thanks @xudong963 !

[codecov-commenter]

Codecov Report

Merging #2860 (ccd37b6) into master (a2da720) will increase coverage by 0.00%.
The diff coverage is 63.88%.

@@           Coverage Diff           @@
##           master    #2860   +/-   ##
=======================================
  Coverage   85.24%   85.25%           
=======================================
  Files         275      275           
  Lines       49002    49001    -1     
=======================================
+ Hits        41773    41775    +2     
+ Misses       7229     7226    -3     

Impacted Files	Coverage Δ
datafusion/sql/src/utils.rs	51.95% <45.45%> (+0.40%)	⬆️
datafusion/core/src/execution/memory_manager.rs	69.95% <50.00%> (-0.31%)	⬇️
datafusion/core/src/datasource/mod.rs	93.93% <100.00%> (ø)
...e/src/physical_optimizer/hash_build_probe_order.rs	89.04% <100.00%> (ø)
datafusion/core/src/physical_plan/sorts/sort.rs	93.09% <100.00%> (ø)
...atafusion/optimizer/src/subquery_filter_to_join.rs	93.90% <100.00%> (ø)
datafusion/physical-expr/src/expressions/case.rs	92.75% <100.00%> (ø)
datafusion/expr/src/logical_plan/plan.rs	74.50% <0.00%> (+0.19%)	⬆️
datafusion/expr/src/window_frame.rs	93.27% <0.00%> (+0.84%)	⬆️

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[alamb]

Thanks @xudong963