CompatHelper: bump compat for MKL in [weakdeps] to 0.8 for package LuxLib, (keep existing compat)

[github-actions]

This pull request changes the compat entry for the MKL package from 0.7 to 0.7, 0.8 for package LuxLib.
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.

[github-actions]

Benchmark Results (ASV)

	main	0b66024...	main/0b6602494c176c...
basics/overhead	0.157 ± 0.011 μs	0.138 ± 0.0018 μs	1.14
time_to_load	0.904 ± 0.0046 s	0.906 ± 0.0061 s	0.997

Benchmark Plots

A plot of the benchmark results have been uploaded as an artifact to the workflow run for this PR.
Go to "Actions"->"Benchmark a pull request"->[the most recent run]->"Artifacts" (at the bottom).