MWPW-156872 - Add no borders variant to Accordion block

[elan-tbx]

• A request has been made to add a no borders option to the Accordion block. Like the variant name implies, this removes the gray separators in between accordion items.
• Note that this has been marked as a critical update in Jira.

Resolves: MWPW-156872

Test URLs:

• Before: https://main--milo--adobecom.hlx.page/drafts/ebartholomew/accordion-no-borders?martech=off
• After: https://ebartholomew-mwpw-156872-no-borders-accordion--milo--adobecom.hlx.page/drafts/ebartholomew/accordion-no-borders?martech=off

[aem-code-sync]

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Commits

• db36ecb ✅ (latest)

[aem-code-sync]

	Page	Scores	Audits	Google
M	/drafts/ebartholomew/accordion-no-borders?martech=off
D	/drafts/ebartholomew/accordion-no-borders?martech=off

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 95.90%. Comparing base (f92f07c) to head (db36ecb).
Report is 8 commits behind head on stage.

Additional details and impacted files

@@            Coverage Diff             @@
##            stage    #2755      +/-   ##
==========================================
+ Coverage   95.88%   95.90%   +0.01%     
==========================================
  Files         173      173              
  Lines       45771    45771              
==========================================
+ Hits        43886    43895       +9     
+ Misses       1885     1876       -9     

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[NadiiaSokolova]

Verified. Ready for Stage.
Testing details https://jira.corp.adobe.com/browse/MWPW-156872