Remove SwiftKeychainWrapper logic

[lougeniaC64]

Removed the remaining SwiftKeychainWrapper logic. This is mostly in the form of license info. As such, the merging of this PR is blocked by the merging of the iOS PR that actually removes the now obsolete library.

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• Breaking changes: This PR follows our breaking change policy
  • This PR follows the breaking change policy:
    • This PR has no breaking API changes, or
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[skhamis]

LGTM!