Remove source/target dropdown header in confirm step of instance migration mode

[pedesen]

Description

The source/target dropdown header can be removed in the confirm step of instance migration mode, because all information is already shown in the notification banner.

TODO

• Remove source/target dropdown header in confirm step
• Keep the dropdown in mapping step

Additional Information

Design issue: https://www.figma.com/design/tnqak7ht4Hb4VCGygvLNFU/Version-Migration-HFW?node-id=2808%3A328364&t=EpWVp0Rz3Aw2Hajq-1

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Acceptance Criteria

• Checked if the specific data needs to be provided for the QA process

Definition of Ready - Checklist

• The issue has a meaningful title, description and testable acceptance criteria
• If documentation needs to be updated, an issue is created in the camunda-docs repo, and the issue is added to our Operate project board.
• If HELM charts need to be updated, an issue is created in the camunda-platform-heml repo, and the issue is added to our Operate project board.
• Potential Security risks have been considered
• Cross-team dependencies have been considered