Update CVODE download URL

[kilicomu]

The CVODE releases have moved to GitHub - download URL has been updated and call to wget has been modified to save the archive to the filename that matches the rest of the installation script.

[spco]

Ugh, looks like Actions images have moved on and no longer supply gfortran 8 out of the box. I can raise a PR to remove gfortran-8 from the matrix of environments, though it would be good in future to continue to run tests on 8.

[spco]

I've remove gfortran-8 from the build matrix - could you rebase and run these again please @kilicomu ?

[codecov]

Codecov Report

Merging #454 (cf2b819) into master (9c06d09) will decrease coverage by 0.04%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #454      +/-   ##
==========================================
- Coverage   65.51%   65.46%   -0.05%     
==========================================
  Files          17       17              
  Lines        2047     2047              
==========================================
- Hits         1341     1340       -1     
- Misses        706      707       +1     

Flag	Coverage Δ
build	52.23% <100.00%> (ø)
tests	82.80% <100.00%> (-0.02%)	⬇️
unittests	31.61% <100.00%> (ø)

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Impacted Files	Coverage Δ
src/atchem2.f90	87.68% <100.00%> (ø)
src/interpolationFunctions.f90	34.09% <0.00%> (-2.28%)	⬇️

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[spco]

Ignore the codecov - it's now garbage. Thanks @kilicomu !