Update DSP compat

[iss2g]

Purpose

This PR extends the compat entries for the DSP package to ensure seamless integration with other packages requiring DSP v0.8+ while preserving backward compatibility.

Changes

• Expanded version bounds in Project.toml for DSP.jl

Testing

• Local tests pass successfully.
• Note: Deprecation warnings were observed, but these are non-critical for current functionality:

  ┌ Warning: `conv(u::AbstractVector{T}, v::AbstractVector{T}, A::AbstractMatrix{T})` is deprecated, use `conv(u, transpose(v), A)` instead.  
  │   caller = derivative7(...) at utilities.jl:262  
  

[peterkovesi]

Thank you for that. I am sure many of the other dependencies need updating too...
I also realize I need to update github actions/cache from v1 to v3 to get the automated CI to run. In the meantime I will merge your PR.
Cheers
Peter