[BUG] cuVS 25.04 benchmark arm64 builds failing: there are no `mkl` arm64 packages

[jameslamb]

Describe the bug

arm64 builds of the cuVS benchmark images are failing like this:

The following packages are incompatible
└─ cuvs-bench-cpu =25.4 * is not installable because there are no viable options
   ├─ cuvs-bench-cpu [25.04.00a87|25.04.00a88|25.04.00a89|25.04.00a91|25.04.00a92] would require
   │  └─ sklearn >=1.5 *, which does not exist (perhaps a missing channel);
   └─ cuvs-bench-cpu 25.04.00a93 would require
      └─ mkl =2023 *, which does not exist (perhaps a missing channel).

(example build link)

Steps/Code to reproduce bug

Look at any recent 25.04 cuVS benchmark builds here.

Expected behavior

N/A

Additional context

There are not any linux-aarch64 builds of mkl on conda-forge (for any verison): https://anaconda.org/conda-forge/mkl/files?version=2023.2.0

Looks like this was introduced by rapidsai/cuvs#260

I guess that this package is never installed in an arm64 environment in cuVS CI, and that suggestions like rapidsai/cuvs#260 (comment) were not applied everywhere