chore/Update some templates WPB-19284

[bbaarriiss]

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PR Submission Checklist for internal contributors

• The PR Title

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

• The PR Description

  • 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?

Issues

"PR opened" notifications are too long and this is making difficult to track notifications in the channel. We decided to give a compact look to the content of the notification.

Solutions

Update the template of PR opened, PR closed (closed without merging and merged cases are shown different now)

Notes (Optional)