CI housekeeping: use the right coveralls client to finalize

[sajith]

We have been using coverallsapp/github-action to send test coverage to coveralls.io, and Python coveralls to indicate test completion. This change switches to using coverallsapp/github-action for the latter also.

Also removes the stale options.packages.find hint from pyproject.toml.

[coveralls]

Pull Request Test Coverage Report for Build 9272901208

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 52.132%

---

Totals
Change from base Build 9181295597:	0.0%
Covered Lines:	738
Relevant Lines:	1446

---

💛 - Coveralls