[MAINTAIN-8] added aria-hidden attribute to 'Add to calendar' link for GroupEx schedule table for all three themes

[aleevas]

Original Issue, this PR is going to fix: MAINTAIN-8 and #898

As was suggested in Jirra issue description i added the aria-hidden attribute for 'Add to caelendar' link in GroupEx schedule page for all three themes

Steps for review

• go to /schedules/group-schedules?location=4435

• Given I have VoiceOver enabled

• When I follow to the icon
  

• screen reader should skip this link

General checks

• All coding styles are fulfilled and there are no any issues reported by CodeSniffer. See Code of Conduct.
• Documentation has been updated according to PR changes.
• Steps for review have been provided according to PR changes.
  
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Thank you for your contribution!

[gundevel]

Can one of the admins verify this patch? Use "o+k to test" or ''t+est this please" for manual build execution.

[hamrant]

ok to test

[gundevel]

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[gundevel]

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