try to fix content size tests again

Author: jamieQ

WorkflowSwiftUI/Tests/PreferredContentSizeTests.swift

@@ -7,7 +7,9 @@ import XCTest
 
 final class PreferredContentSizeTests: XCTestCase {
     func test_preferredContentSize() throws {
-        guard #unavailable(iOS 18.0) else {
+        // FIXME: actually solve whatever the problem is here
+        let osMajorVersion = ProcessInfo.processInfo.operatingSystemVersion.majorVersion
+        guard osMajorVersion < 18 else {
             try XCTSkipIf(true, "Intrinsic content size does not update unless hosted in an actual app on iOS 18")
             return
         }