ci(swift): use PR branch to test swift integration rather than version

[russellwheatley]

Description

• Using version isn't a good idea particularly if there is an update to the code without a version. Preferable to test against any changes in the pull request.

Related Issues

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Checklist

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This will ensure a smooth and quick review process. Updating the pubspec.yaml and changelogs is not required.

• I read the Contributor Guide and followed the process outlined there for submitting PRs.
• My PR includes unit or integration tests for all changed/updated/fixed behaviors (See Contributor Guide).
• All existing and new tests are passing.
• I updated/added relevant documentation (doc comments with ///).
• The analyzer (melos run analyze) does not report any problems on my PR.
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Breaking Change

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• Yes, this is a breaking change.
• No, this is not a breaking change.