Doc/Michelson: redirect unit and boolean operations to interactive reference.

Context

Answers this part of #4077:

• delete the parts about instructions from the static reference:
  • Operations on type unit
  • Operations on booleans

The documentation about all the operations on unit and bool in the interactive reference contains that found in the static reference.
The inclusion was checked manually by comparing the static and interactive documentations for each comparison instruction of the static reference.

Manually testing the MR

make -C docs -j

And then open docs/_build/alpha/michelson.html in a web browser.

Checklist

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