fix: non-sendable

[vladdeSV]

This "solves" the warning on the load() method, see #27:

Instance methods of non-Sendable types cannot be marked as 'https://github.com/sendable'; this is an error in Swift 6

However, I am unsure of the implications of removing the @Sendable attribute 🤷‍♂️.

Solution provided by https://github.com/lorenzofiamingo/swiftui-cached-async-image/issues/27#issuecomment-2114089315 .