Bump VERSION to 1.5.9 #699

Job	Run time
Build (x64-mingw-ucrt)	5m 57s
Build (x64-mingw-ucrt)	5m 57s
Build (x64-mingw-ucrt)	5m 57s
Build (x64-mingw32)	5m 57s
Build (x64-mingw32)	5m 57s
Build (x64-mingw32)	5m 57s
Build (x86-mingw32)	2m 14s
Build (x86-mingw32)	2m 5s
Build (x86-mingw32)	5m 8s
Test	0s
Test	0s
Test (windows-latest, 3.3, x64-mingw-ucrt, 17.0-1-windows-x64)	4m 59s
Test (windows-latest, 3.1.4-1, x86-mingw32, 10.20-1-windows)	5m 58s
Test (windows-latest, 2.5, x64-mingw32, 10.20-1-windows)	6m 4s
	1h 2m 10s

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