feat(accordion): revert changes for accordion key nav support

[EvilAlexei]

Because of breaking changes need to revert new html structure of accordion, main template and Custom html demo.

• Revert accordion component template, changed button to div
• Revert accordion demo Custom html, changed button to div

Actual result:

Expected result:

PR Checklist

Before creating new PR, please take a look at checklist below to make sure that you've done everything that needs to be done before we can merge it.

• read and followed the CONTRIBUTING.md guide.
• built and tested the changes locally.
• added/updated tests.
• added/updated API documentation.
• added/updated demos.

[codecov]

Codecov Report

Merging #4093 into development will decrease coverage by 0.06%.
The diff coverage is n/a.

@@               Coverage Diff               @@
##           development    #4093      +/-   ##
===============================================
- Coverage        72.23%   72.17%   -0.07%     
===============================================
  Files              252      252              
  Lines             8237     8237              
  Branches          1565     1565              
===============================================
- Hits              5950     5945       -5     
- Misses            1866     1868       +2     
- Partials           421      424       +3

Impacted Files	Coverage Δ
src/chronos/i18n/it.ts	71.42% <0%> (-28.58%)	⬇️
src/chronos/i18n/pl.ts	72.22% <0%> (-5.56%)	⬇️
src/chronos/i18n/uk.ts	78.04% <0%> (-2.44%)	⬇️

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[YevheniiaMazur]

Tested, looks good