Fix conversion warning on chrono.h #7480

Job	Run time
build (windows-2019, Win32, v142, 17, Debug)	1m 56s
build (windows-2019, Win32, v142, 17, Release)	2m 47s
build (windows-2019, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 5s
build (windows-2019, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 25s
build (windows-2019, x64, v141, 14, Debug)	1m 15s
build (windows-2019, x64, v141, 14, Release)	2m 37s
build (windows-2019, x64, v141, 17, Debug)	1m 17s
build (windows-2019, x64, v141, 17, Release)	2m 11s
build (windows-2019, x64, v142, 17, Debug)	1m 33s
build (windows-2019, x64, v142, 17, Release)	2m 4s
build (windows-2019, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 8s
build (windows-2019, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 20s
build (windows-2019, x64, v142, 20, Debug)	1m 51s
build (windows-2019, x64, v142, 20, Release)	3m 19s
mingw (mingw64)	3m 59s
build (windows-2022, x64, v143, Debug, 20)	2m 21s
mingw (ucrt64)	3m 55s
	38m 3s

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