Update README for clarity on performance comparison #8788

Job	Run time
mingw (mingw64)	4m 17s
mingw (ucrt64)	4m 1s
build (windows-2022, Win32, v142, 17, Debug)	1m 14s
build (windows-2022, x64, v142, 17, Release)	2m 12s
build (windows-2022, x64, v142, 17, Debug)	1m 11s
build (windows-2022, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	1m 53s
build (windows-2022, Win32, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 8s
build (windows-2022, Win32, v142, 17, Release)	2m 4s
build (windows-2022, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Release)	2m 2s
build (windows-2022, x64, v142, 20, Release)	2m 52s
build (windows-2022, x64, v142, 17, -DBUILD_SHARED_LIBS=ON, Debug)	1m 6s
build (windows-2022, x64, v143, Debug, 20)	1m 44s
build (windows-2022, x64, v142, 20, Debug)	1m 34s
	27m 18s

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