Removed compas_rhino.install v8 flag

[chenkasirer]

Part of #1351.

Removing support for the v8.0 flag from compas_rhino.install to alleviate some of the confusion around using COMPAS in Rhino8.

The supported procedure is https://compas.dev/compas/latest/userguide/cad.rhino8.html.

What type of change is this?

• Bug fix in a backwards-compatible manner.
• New feature in a backwards-compatible manner.
• Breaking change: bug fix or new feature that involve incompatible API changes.
• Other (e.g. doc update, configuration, etc)

Checklist

Put an x in the boxes that apply. You can also fill these out after creating the PR. If you're unsure about any of them, don't hesitate to ask. We're here to help! This is simply a reminder of what we are going to look for before merging your code.

• I added a line to the CHANGELOG.md file in the Unreleased section under the most fitting heading (e.g. Added, Changed, Removed).
• I ran all tests on my computer and it's all green (i.e. invoke test).
• I ran lint on my computer and there are no errors (i.e. invoke lint).
• I added new functions/classes and made them available on a second-level import, e.g. compas.datastructures.Mesh.
• I have added tests that prove my fix is effective or that my feature works.
• I have added necessary documentation (if appropriate)

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 61.75%. Comparing base (7ea3fbd) to head (5f3fc63).
Report is 15 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1423      +/-   ##
==========================================
- Coverage   61.77%   61.75%   -0.02%     
==========================================
  Files         207      207              
  Lines       22300    22300              
==========================================
- Hits        13775    13771       -4     
- Misses       8525     8529       +4     

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[chenkasirer]

added to #1427