Fix bug with rounding with zoned RelativeTo and increment #2161

Job	Run time
Test FFI (stable, ubuntu-latest)	25s
Test (stable, ubuntu-latest)	29s
Documentation	24s
MSRV	25s
Test (stable, macos-latest)	34s
Lint	43s
Test (stable, windows-latest)	1m 27s
Test feature matrix	12m 52s
	17m 19s

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