CI: bump actions versions to use node.js 20 where applicable. #620

Job	Run time
Windows-2019 [arch x64, toolset v142, backend botan, build shared libs off, use CMake prefix path on, sanitizers off]	35m 24s
Windows-2019 [arch x64, toolset v142, backend botan, build shared libs off, use CMake prefix path off, sanitizers off]	37m 55s
Windows-2019 [arch x64, toolset v142, backend openssl, build shared libs off, use CMake prefix path on, sanitizers off]	21m 39s
Windows-2019 [arch x64, toolset v142, backend openssl, build shared libs off, use CMake prefix path off, sanitizers off]	22m 5s
Windows-2019 [arch x64, toolset ClangCL, backend botan, build shared libs off, use CMake prefix path on, sanitizers off]	37m 34s
Windows-2019 [arch x64, toolset ClangCL, backend botan, build shared libs off, use CMake prefix path off, sanitizers off]	42m 11s
Windows-2019 [arch x64, toolset ClangCL, backend openssl, build shared libs off, use CMake prefix path on, sanitizers off]	23m 13s
Windows-2019 [arch x64, toolset ClangCL, backend openssl, build shared libs off, use CMake prefix path off, sanitizers off]	23m 59s
Windows-2019 [arch x64, toolset v142, backend botan, build shared libs off, use CMake prefix path off, sanitizers on]	49m 51s
Windows-2019 [arch Win32, toolset ClangCL, backend botan, build shared libs off, use CMake prefix path on, sanitizers off]	38m 59s
Windows-2019 [arch Win32, toolset v142, backend openssl, build shared libs off, use CMake prefix path off, sanitizers off]	24m 39s
	5h 57m 29s

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