bump version number to 4.3.3-SNAPSHOT for development

[isaacbrodsky]

cc @nrabinowitz @dmitryzv

[coveralls]

Pull Request Test Coverage Report for Build #574

Details

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 94.437%

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Totals
Change from base Build #572:	0.0%
Covered Lines:	523
Relevant Lines:	546

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💛 - Coveralls

[dfellis]

Perhaps we should see if there's a github action to automatically do this on a release?

[isaacbrodsky]

There actually is in the CI script, but it's disabled because PR-and-review-required is enabled on this repo, and the script wasn't set up to bypass that.