[CI] Change concurrency group naming (Issue #3301)

[IAlibay]

Fixes #3301

Changes made in this Pull Request:

• Changes the concurrency group to "${{ github.ref }}-${{ github.head_ref }}"
  This means that for commits to develop, the group will be set to refs/heads/develop, so any other CI jobs running from a commit will be cancelled and this will run instead.
  For a PR (let's say this one), the group will be named refs/pull/3302/merge-fix-3301, so it will only kill CI jobs within that PR with the same group name.

Note: I tried checking if an external group collision could happen, thankfully it looks like that's not possible.

PR Checklist

• Tests?
• Docs?
• CHANGELOG updated?
• Issue raised/referenced?

[codecov]

Codecov Report

Merging #3302 (7ae50a6) into develop (80ce50d) will increase coverage by 3.98%.
The diff coverage is n/a.

@@             Coverage Diff             @@
##           develop    #3302      +/-   ##
===========================================
+ Coverage    89.59%   93.58%   +3.98%     
===========================================
  Files          167      176       +9     
  Lines        21401    22883    +1482     
  Branches         0     3195    +3195     
===========================================
+ Hits         19175    21414    +2239     
+ Misses        2226     1418     -808     
- Partials         0       51      +51     

Impacted Files	Coverage Δ
package/MDAnalysis/lib/formats/libmdaxdr.pyx	89.81% <0.00%> (ø)
package/MDAnalysis/lib/_cutil.pyx	100.00% <0.00%> (ø)
package/MDAnalysis/lib/c_distances.pyx	100.00% <0.00%> (ø)
package/MDAnalysis/lib/qcprot.pyx	100.00% <0.00%> (ø)
package/MDAnalysis/lib/nsgrid.pyx	91.30% <0.00%> (ø)
package/MDAnalysis/lib/_augment.pyx	100.00% <0.00%> (ø)
package/MDAnalysis/lib/formats/cython_util.pyx	100.00% <0.00%> (ø)
package/MDAnalysis/lib/c_distances_openmp.pyx	100.00% <0.00%> (ø)
package/MDAnalysis/lib/formats/libdcd.pyx	88.48% <0.00%> (ø)
package/MDAnalysis/coordinates/base.py	95.24% <0.00%> (+0.12%)	⬆️
... and 14 more

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