Fix conversion warning on chrono.h #7479

Job	Run time
build (windows-2019, Win32, v142, 17, Debug)	2m 20s
build (windows-2019, Win32, v142, 17, Release)	2m 13s
build (windows-2019, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 29s
build (windows-2019, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	1m 50s
build (windows-2019, x64, v141, 14, Debug)	1m 33s
build (windows-2019, x64, v141, 14, Release)	2m 15s
build (windows-2019, x64, v141, 17, Debug)	1m 59s
mingw (mingw64)	4m 2s
build (windows-2019, x64, v141, 17, Release)	2m 44s
mingw (ucrt64)	3m 47s
build (windows-2019, x64, v142, 17, Debug)	1m 13s
build (windows-2019, x64, v142, 17, Release)	2m 17s
build (windows-2019, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 56s
build (windows-2019, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	3m 7s
build (windows-2019, x64, v142, 20, Debug)	2m 18s
build (windows-2019, x64, v142, 20, Release)	3m 16s
build (windows-2022, x64, v143, Debug, 20)	2m 12s
	40m 31s

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