Use python3 in fuzzing/build.sh #513

Job	Run time
macos / Test macOS	1m 0s
windows / Test Windows	2m 1s
ci / Build	3m 27s
ci / Lint	1m 9s
ci / Test (0)	6m 23s
ci / Test (1)	8m 28s
ci / Test (2)	6m 38s
ci / Test (3)	9m 58s
ci / Test (4)	4m 44s
ci / Test (5)	5m 43s
ci / Test (6)	4m 40s
ci / Test (7)	6m 7s
ci / Test (8)	4m 18s
ci / Test (9)	4m 30s
ci / Publish Unit Tests Results	1s
	1h 9m 7s

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