Cannot `import cv2` in Python tests despite following knowledge base

### Conda-forge documentation

- [X] I could not solve my problem using the conda-forge documentation.

### Installed packages

```shell
N/A
```

### Environment info

```shell
Conda forge feedstock CI
```

### Issue

(I'm filing this issue here largely because I don't know of a better place to file it; feel free to let me know of one.)

I'm a maintainer of https://github.com/conda-forge/dandi-feedstock, which uses opencv in some of its tests, and the `recipe/` folder contains a `yum_requirements.txt` file for the opencv deps as described at https://conda-forge.org/docs/maintainer/knowledge_base/#libgl. However, ever since the feedstock's v0.61.0 PR on March 19 (the previous update PR, which was successful, being on February 29), the opencv-using tests have been failing with "ImportError: libEGL.so.1: cannot open shared object file: No such file or directory".

I asked about this on Gitter on March 21, but the only advice I got was to add `mesa-libEGL` to `yum_requirements.txt`; at the time, I failed to rerender after applying this change, and so I didn't get anywhere. Re-attemping it now, when I add `mesa-libEGL` and rerender, this just results in "libEGL.so.1" in the error message being replaced with "libOpenGL.so.0". I tried blindly adding `mesa-libOpenGL` to `yum_requirements.txt` and rerendering, but that didn't help, and now I don't know what to do.