Add visionOS to SPM Package definition

[philipphofmann]

VisionOS has been available since Swift tools version 5.9, see PR. We can only add it as an official platform to our SPM definition when bumping the Swift tools version to 5.9. Our current version is

sentry-cocoa/Package.swift

Line 1 in 2124551

// swift-tools-version:5.3

[brustolin]

Since visionOS is in its first version, we don't need to add it to the Package definition, Its already working properly.