ci: Report coverage to Codecov without token

[matthewfeickert]

Description

Resolves #1559

This should actually resolve Issue #1559 by using the tokenless infrastructure that Codecov now supports (c.f. codecov/codecov-action#29 (comment)).

This infrastructure has already existed, but in newer versions of the GitHub Action it is supposed to work better, so we'll see how quickly the coverage report comes in.

(cc @alexander-held as this has been an Issue for cabinetry in the past I think).

Checklist Before Requesting Reviewer

• Tests are passing
• "WIP" removed from the title of the pull request
• Selected an Assignee for the PR to be responsible for the log summary

Before Merging

For the PR Assignees:

• Summarize commit messages into a comprehensive review of the PR

* Report coverage to Codecov without using a secret Codecov token
   - c.f. https://github.com/codecov/codecov-action/issues/29#issuecomment-595288709
   - Effectively reverts Codecov logic part of PR #1622
* Ensure codecov/codecov-action v2 used
   - Amends PR #1623

[codecov]

Codecov Report

Merging #1628 (cbb02cb) into master (e47b1cf) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master    #1628   +/-   ##
=======================================
  Coverage   97.70%   97.70%           
=======================================
  Files          63       63           
  Lines        4048     4048           
  Branches      576      576           
=======================================
  Hits         3955     3955           
  Misses         54       54           
  Partials       39       39           

Flag	Coverage Δ
contrib	25.44% <ø> (ø)
unittests	97.48% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

Continue to review full report at Codecov.

Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update e47b1cf...cbb02cb. Read the comment docs.

[matthewfeickert]

@alexander-held with the codecov/codecov-action@v2 GHA things seem to work fine without a token. 👍

[alexander-held]

That's great! I had removed it previously for cabinetry (scikit-hep/cabinetry#215) and added it back again later (scikit-hep/cabinetry#230) due to an error that occurred. Reports seemed to be slightly slower without the token when I tried it, but this was all with the old version — I should give the new one a try, thanks!