Bump default BioC version to 3.21. #8082

Job	Run time
Linux (gcc, debian:stable, intel)	34m 44s
Linux (gcc, debian:stable, arm)	30m 2s
Linux (gcc, debian:testing, intel)	33m 44s
Linux (gcc, debian:testing, arm)	30m 54s
MacOS (macOS-13)	47m 43s
Linux (clang, debian:stable, intel)	34m 49s
MacOS (macOS-14)	19m 31s
Windows (check)	52m 1s
Linux (clang, debian:stable, arm)	30m 42s
Windows (installer)	20m 44s
Linux (clang, debian:testing, intel)	35m 33s
Linux (clang, debian:testing, arm)	30m 45s
	6h 41m 12s

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