fix(service): return project version as int

[olevski]

/deploy #persist

closes #3569

[RenkuBot]

You can access the deployment of this PR at https://renku-ci-rp-3591.dev.renku.ch

[olevski]

If you visit: https://renku-ci-rp-3591.dev.renku.ch/api/renku/apiversion

The result has an integer instead of a float:

{"result":{"latest_version":"2.7.0.dev3+g12f73dd5","maximum_api_version":"2.1","minimum_api_version":"1.0","supported_project_version":10}}

[coveralls]

Pull Request Test Coverage Report for Build 5931149270

• 1 of 1 (100.0%) changed or added relevant line in 1 file are covered.
• 3 unchanged lines in 3 files lost coverage.
• Overall coverage increased (+0.01%) to 85.731%

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Files with Coverage Reduction	New Missed Lines	%
renku/core/migration/m_0003__1_jsonld.py	1	87.68%
renku/ui/cli/init.py	1	96.9%
renku/ui/cli/service.py	1	67.72%

Totals
Change from base Build 5900967698:	0.01%
Covered Lines:	25853
Relevant Lines:	30156

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💛 - Coveralls