Add default version to `version_string` function #3149

Job	Run time
Check Access Permissions	2s
Check Packages and Shards	1m 25s
Mutation Testing - Normal, Stackslib	2h 40m 7s
Mutation Testing - Normal, Stacks Node	23m 28s
Mutation Testing - Shards, Small	0s
Mutation Testing - Shards, Stackslib	0s
Mutation Testing - Normal, Small	0s
Mutation Testing - Shards, Stacks Node	0s
Mutation Testing - Normal, Stacks Signer	0s
Output Mutants	5s
	3h 5m 7s

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