Update the required libvalkey-py version to 4.0.0

[mkmkme]

Pull Request check-list

Please make sure to review and check all of these items:

• Do tests and lints pass with this change?
• Do the CI tests pass with this change (enable it first in your forked repo and wait for the github action build to finish)?
• Is the new or changed code fully tested?
• Is a documentation update included (if this change modifies existing APIs, or introduces new ones)?
• Is there an example added to the examples folder (if applicable)?

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Description of change

Previously, the required libvalkey-py version contained "beta 1" version. Now the proper 4.0.0 was released, use it instead.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.11%. Comparing base (0592263) to head (6b0cfcb).

Additional details and impacted files

@@           Coverage Diff           @@
##             main      #73   +/-   ##
=======================================
  Coverage   75.11%   75.11%           
=======================================
  Files         132      132           
  Lines       34405    34405           
=======================================
  Hits        25845    25845           
  Misses       8560     8560           

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