[#370] Fixed sub-navigation active tabindex.

[febdao]

Checklist before requesting a review

• I have formatted the subject to include the issue number
  as [#123] Verb in past tense with a period at the end.
• I have provided information in the Changed section about WHY something was
  done if this was a bespoke implementation.
• I have performed a self-review of my code.
• I have commented on my code, particularly in hard-to-understand areas.
• I have added tests that prove my fix is effective or that my feature works.
• I have run new and existing relevant tests locally with my changes,
  and they have passed.
• I have provided screenshots, where applicable.

Changed

1. Fixed sub-navigation active tabindex.

Screenshots

[github-actions]

🚀 Deployed on https://6730b2f28109c6cacc87a68f--civictheme-uikit.netlify.app

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 1 line in your changes missing coverage. Please review.

Project coverage is 13.87%. Comparing base (a6ccd6f) to head (67d43d5).
Report is 4 commits behind head on main.

Files with missing lines	Patch %	Lines
components/00-base/collapsible/collapsible.js	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #423   +/-   ##
=======================================
  Coverage   13.87%   13.87%           
=======================================
  Files          27       27           
  Lines        1290     1290           
  Branches      307      307           
=======================================
  Hits          179      179           
  Misses        894      894           
  Partials      217      217           

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