Update Coveralls action in CI workflow

[ranocha]

As mentioned by @DanielDoehring in #3084 (comment), the coveralls GitHub action did not report results in many recent runs (including PRs). The latest CI run on main where it shows up successfully is 42b5759 with coveralls results https://coveralls.io/builds/79945251.

Here, I updated some settings to avoid deprecated functionality. It looks like this helps - at least in this PR.

Closes #3085.

[github-actions]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 96.89%. Comparing base (7acbb05) to head (9c7b37d).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #3086   +/-   ##
=======================================
  Coverage   96.89%   96.89%           
=======================================
  Files         647      647           
  Lines       50024    50024           
=======================================
  Hits        48466    48466           
  Misses       1558     1558           

Flag	Coverage Δ
unittests	96.89% <ø> (ø)

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[DanielDoehring]

Hm, but something else is now not working 🤔

[ranocha]

Documenter.jl is configured not to run when changes are made only to the CI workflow file, see

Trixi.jl/.github/workflows/Documenter.yml

Line 11 in 7acbb05

- '.github/workflows/ci.yml'

[ranocha]

Thanks for your review! Let's see whether this fixes the issues.