ACC-270 [iOS] Fix labels and headings

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PR Submission Checklist for internal contributors

• The PR Title

  • [x] conforms to the style of semantic commits messages¹ supported in Wire's Github Workflow²
  • [x] contains a reference JIRA issue number like SQPIT-764
  • [x] answers the question: If merged, this PR will: ... ³

• The PR Description

  • [x] is free of optional paragraphs and you have filled the relevant parts to the best of your ability

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What's new in this PR?

In this PR, voice over issues have been fixed in:

• Conversations list
• Contacts list
• Connection
• CheckmarkCell

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PR Post Submission Checklist for internal contributors (Optional)

• [x] Wire's Github Workflow has automatically linked the PR to a JIRA issue

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PR Post Merge Checklist for internal contributors

• [ ] If any soft of configuration variable was introduced by this PR, it has been added to the relevant documents and the CI jobs have been updated.

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References

1. https://sparkbox.com/foundry/semantic_commit_messages
2. https://github.com/wireapp/.github#usage
3. E.g. feat(conversation-list): Sort conversations by most emojis in the title #SQPIT-764.

Codecov Report

Merging #5865 (286a969) into develop (560ab15) will increase coverage by 0.04%. The diff coverage is 85.60%.

:exclamation: Current head 286a969 differs from pull request most recent head 4dbecd0. Consider uploading reports for the commit 4dbecd0 to get more accurate results

@@             Coverage Diff             @@
##           develop    #5865      +/-   ##
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+ Coverage    60.58%   60.63%   +0.04%     
===========================================
  Files         1026     1026              
  Lines        57048    57232     +184     
  Branches     23686    23730      +44     
===========================================
+ Hits         34564    34702     +138     
- Misses       22108    22153      +45     
- Partials       376      377       +1