`diagnose-api-breaking-changes` reports `package`-level access modifiers

[Joannis]

Description

In a recent Hummingbird PR we've had a package enum containing types of errors we throw. While adding a enum case to this enum, a breaking change was incorrectly reported.

Reproduction

package enum MyError: Error {
  case initialErrorCase
  
  // Added later
  case addedErrorCase
}

Expected behavior

I expect this change not to be reported as breaking.

Environment

Apple Swift version 6.0.3 (swift-6.0.3-RELEASE)
Target: arm64-apple-macosx15.0

Additional information

No response