Update codecov config with new github org

[taylanisikdemir]

What changed?
Repo has moved from uber-go/cadence-client to cadence-workflow/cadence-go-client

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 82.28%. Comparing base (f8bfb87) to head (63369ad).
Report is 1 commits behind head on master.

see 2 files with indirect coverage changes

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