remove Octavian and matmul!

[jlchan]

Would address https://github.com/trixi-framework/Trixi.jl/issues/1906, and is the first step in addressing https://github.com/trixi-framework/Trixi.jl/issues/1789.

[github-actions[bot]]

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[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 96.15%. Comparing base (887bab9) to head (9a567d7).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## jc/dev_DGMulti #1950 +/- ## =============================================== Coverage 96.15% 96.15% =============================================== Files 454 454 Lines 36509 36509 =============================================== + Hits 35102 35103 +1 + Misses 1407 1406 -1 ``` | [Flag](https://app.codecov.io/gh/trixi-framework/Trixi.jl/pull/1950/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/trixi-framework/Trixi.jl/pull/1950/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework) | `96.15% <100.00%> (+<0.01%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework#carryforward-flags-in-the-pull-request-comment) to find out more.

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[jlchan]

@ranocha @JoshuaLampert I requested your reviews since you both commented on #1789. I am planning on merging PRs associated with this in a staging branch, and thought this might make it easier to review than a single large PR.

Let me know if you'd prefer to proceed otherwise

[jlchan]

Is the MPI-macos test failure due to the Codecov issue when the PR is from a fork of the repo?

[ranocha]

Is the MPI-macos test failure due to the Codecov issue when the PR is from a fork of the repo?

Yes, exactly. It would be easier if you could make the PRs from branches in the main repo

[JoshuaLampert]

Thanks for taking care of this @jlchan!