refactor(Init): fix unbounded variable in _ask_tag_format

[bearomorphism]

Description

Before this change, the type of tag_format is Any | Unbounded | str at the end of the function. Actually tag_format is defined for all code paths.

• If is_correct_format is True, then tag_format is assigned "v$version" and the function returns it.
• If is_correct_format is False, then tag_format is initialized in the if-block.

The function logic should be easier to understand after this change.

Checklist

• I have read the contributing guidelines

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

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Additional details and impacted files

@@              Coverage Diff               @@
##             v4-9-0-test    #1529   +/-   ##
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  Coverage               ?   98.07%           
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  Files                  ?       58           
  Lines                  ?     2700           
  Branches               ?        0           
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  Hits                   ?     2648           
  Misses                 ?       52           
  Partials               ?        0           

Flag	Coverage Δ
unittests	98.07% <100.00%> (?)

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