CompatHelper: bump compat for ClassicalOrthogonalPolynomials to 0.8, (keep existing compat)

[github-actions[bot]]

This pull request changes the compat entry for the ClassicalOrthogonalPolynomials package from 0.7 to 0.7, 0.8. This keeps the compat entries for earlier versions.

Note: I have not tested your package with this new compat entry. It is your responsibility to make sure that your package tests pass before you merge this pull request.

[codecov[bot]]

Codecov Report

Patch coverage: 100.00% and no project coverage change.

Comparison is base (c6efa38) 96.21% compared to head (8a3a98b) 96.21%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #148 +/- ## ======================================= Coverage 96.21% 96.21% ======================================= Files 6 6 Lines 846 846 ======================================= Hits 814 814 Misses 32 32 ``` | [Impacted Files](https://codecov.io/gh/JuliaApproximation/MultivariateOrthogonalPolynomials.jl/pull/148?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation) | Coverage Δ | | |---|---|---| | [src/rect.jl](https://codecov.io/gh/JuliaApproximation/MultivariateOrthogonalPolynomials.jl/pull/148?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL3JlY3Quamw=) | `94.82% <100.00%> (ø)` | |

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