cp: fix 2 clippy expections

[oech3]

remove clippy::if_not_else and clippy::unnecessary_cast allow(unused_variables)

[RenjiSann]

Also, it seems that you kept clippy::unnecessary_cast after all, is it expected ?

[oech3]

I typo. I meant allow(unused_variables)

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/tail/symlink (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/dd/no-allocate is now being skipped but was previously passing.
Congrats! The gnu test tests/seq/seq-epipe is now passing!
Note: The gnu test tests/misc/write-errors was skipped on 'main' but is now failing.

[codspeed-hq]

Merging this PR will not alter performance

✅ 345 untouched benchmarks
⏩ 46 skipped benchmarks¹

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_{Comparing oech3:cp-if-not-else (e65084d) with main (8aa2c06)}

Footnotes

1. 46 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩