[#10328] Remove coveralls as not used. Update codecov.io reporting version.

[adiroiban]

Scope and purpose

This tries to get CI green ... spring is coming :)

Update codecov actions script to v2 . V3 was failing.
Removed coveralls reporting as we were not using it.

Contributor Checklist:

• The associated ticket in Trac is here: https://twistedmatrix.com/trac/ticket/10328
• [NA] I ran tox -e lint to format my patch to meet the Twisted Coding Standard
• I have created a newsfragment in src/twisted/newsfragments/ (see: News files)
• The title of the PR starts with the associated Trac ticket number (without the # character).
• [NA] I have updated the automated tests and checked that all checks for the PR are green.
• I have submitted the associated Trac ticket for review by adding the word review to the keywords field in Trac, and putting a link to this PR in the comment; it shows up in https://twisted.reviews/ now.
• The merge commit will use the below format
  The first line is automatically generated by GitHub based on PR ID and branch name.
  The other lines generated by GitHub should be replaced.

Merge pull request #123 from twisted/4356-branch-name-with-trac-id

Author: adiroibam
Reviewer: 
Fixes: ticket:10238

Fix the CI build system to have green runs.
Use codecov action v2 to publish coverage.
Remove publishing to coveralls.

[exarkun]

On most projects where I've seen codecov used, codecov posts a comment on PRs. I don't see such a comment on this PR though. Working as intended?

[adiroiban]

hm... I see the coverage reports pushed at https://codecov.io/gh/twisted/twisted/commit/6eb7be783c15d4304b12ef25a0aa10dc2f9632b2/build

but yes. there is no commit status check report :(

Looks like this is due to the fact that Azure CI are no longer reported....and codecov.io was configured to wait for 15 other CI builds before reporting the results... to reduce confusion due to partial reports

[exarkun]

If you file a ticket about how Windows CI is broken and needs fixing then I think I'm happy to approve this PR.

[adiroiban]

Ticket created here https://twistedmatrix.com/trac/ticket/10331

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It looks like there is a PR to move Windows runs on GHA but it has no ticket

#1647

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Looks like Azure tests stopped working since #1681

The previous commit had the Azure test running, and in PR 1681 the Azure config was updated...

[exarkun]

... the joy of manually counting small numbers of things because the computer cannot manage to do it ...