build(deps): bump actions/download-artifact from 4 to 6 #375

Job	Run time
code-format	34s
check_vvl	1m 46s
linux (address sanitizer, release, custom_hash_map OFF )	44m 49s
linux (address sanitizer, release, custom_hash_map ON )	46m 14s
linux (thread sanitizer, release, custom_hash_map ON )	4m 50s
linux (undefined behavior sanitizer, debug)	20m 33s
Ubuntu Backcompat	7m 54s
windows (amd64)	27m 17s
windows (amd64_x86)	28m 28s
mingw	1m 24s
	3h 3m 49s

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