Remove deprecation note from ListLookup

[carlosedp]

The comment on ListLookup documentation does not reflect current use of the API. As seen, the it's a pattern in use for Decoders on multiple cores like:

• DinoCPU: https://github.com/jlpteaching/dinocpu/blob/124cc110410f7daae924301c1e33157f6b02d3d5/src/main/scala/components/control.scala#L50
• ChiselV: https://github.com/carlosedp/chiselv/blob/f73d654b2d50546d87e565ca4b152871d572fec8/src/main/scala/Decoder.scala#L29
• Chiselwatt: https://github.com/antonblanchard/chiselwatt/blob/c8336341125c146336b2ddfb104382733e08fc19/src/main/scala/Control.scala#L296

And many others.

Contributor Checklist

• Did you add Scaladoc to every public function/method?
• Did you add at least one test demonstrating the PR?
• Did you delete any extraneous printlns/debugging code?
• Did you specify the type of improvement?
• Did you add appropriate documentation in docs/src?
• Did you state the API impact?
• Did you specify the code generation impact?
• Did you request a desired merge strategy?
• Did you add text to be included in the Release Notes for this change?

Type of Improvement

• documentation

API Impact

No impact, documentation change.

Backend Code Generation Impact

No impact.

Desired Merge Strategy

• Squash: The PR will be squashed and merged (choose this if you have no preference.

Release Notes

Reviewer Checklist (only modified by reviewer)

• Did you add the appropriate labels?
• Did you mark the proper milestone (Bug fix: 3.3.x, [small] API extension: 3.4.x, API modification or big change: 3.5.0)?
• Did you review?
• Did you check whether all relevant Contributor checkboxes have been checked?
• Did you mark as Please Merge?

[sequencer]

I'd like to deprecate this API, asking user switching to decoder API. Since this API will introduce a cascade Mux rather than parallel pla, which can be the critical path in most of CPU designs. So I still encourage designers switching to decoder for the this performance issue.

[ekiwi]

@sequencer Would you mind making a PR on @carlosedp chiselv design to show how to move to the decoder API? Then we could always point people to your change to show how to migrate.

[sequencer]

carlosedp/chiselv#2 is sent.

[sequencer]

A deprecation PR #2259 is sent, fell free to open this if @carlosedp has more questions ;p