force new FFMPEG.jl version for tests

[ranocha]

This should fix our recent CI failures on Windows and macOS related to ancient versions of FFMPEG, e.g.,

• https://github.com/trixi-framework/Trixi.jl/actions/runs/8170243302/job/22336021936?pr=1857#step:7:45
• https://github.com/trixi-framework/Trixi.jl/actions/runs/8170243302/job/22336022461?pr=1857#step:7:45

It looks like the reason is that the package manager prefers a newer version of FFMPEG_jll that is not yet allowed by FFMPEG.jl (but there is the PR https://github.com/JuliaIO/FFMPEG.jl/pull/59): I was able to reproduce getting the old version as follows.

1. Remove Manifest.toml and use the current clone of Trixi.jl
2. julia +1.9 --project=.
3. (Trixi) pkg> build
4. julia> ENV["TRIXI_TEST"] = "none"
5. (Trixi) pkg> test Trixi

Then, I inspected the generated Manifest.toml:

(debug) pkg> status --manifest --outdated
Status `debug/Manifest.toml`
...
⌃ [c87230d0] FFMPEG v0.2.4 (<v0.4.1)

Updating yields

(debug) pkg> add FFMPEG@v0.4
   Resolving package versions...
    Updating `debug/Project.toml`
  [c87230d0] + FFMPEG v0.4.1
    Updating `debug/Manifest.toml`
  [b99e7846] - BinaryProvider v0.5.10
  [c87230d0] ↑ FFMPEG v0.2.4 ⇒ v0.4.1
⌅ [b22a6f82] ↓ FFMPEG_jll v6.1.1+0 ⇒ v4.4.4+1

Let's see whether it works.

Closes #1852

[github-actions[bot]]

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Created with :heart: by the Trixi.jl community.

[ranocha]

CI is still running, so it looks like this hotfix works for now.

[codecov[bot]]

Codecov Report

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

Project coverage is 96.28%. Comparing base (e205b06) to head (3364410). Report is 3 commits behind head on main.

Additional details and impacted files

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