Adjust API Availability for Structured Concurrency Backport (#18)

* Change API availability for concurrency backport

* adjust the availability check

Co-authored-by: Konrad `ktoso` Malawski <[email protected]>
Co-authored-by: Konrad `ktoso` Malawski <[email protected]>

Author: moritzsternemann

Sources/InstrumentationBaggage/Baggage.swift

@@ -224,8 +224,8 @@ extension Baggage {
 
 // MARK: - Propagating Baggage
 
-#if swift(>=5.5)
-@available(macOS 12.0, iOS 15.0, watchOS 8.0, tvOS 15.0, *)
+#if swift(>=5.5) && canImport(_Concurrency)
+@available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *)
 extension Baggage {
     /// A `Baggage` automatically propagated through task-local storage. This API enables binding a top-level `Baggage` and passing it
     /// implicitly to any child tasks when using structured concurrency.

Tests/InstrumentationBaggageTests/BaggageTests.swift

@@ -63,8 +63,8 @@ final class BaggageTests: XCTestCase {
     }
 
     func test_automaticPropagationThroughTaskLocal() throws {
-        #if swift(>=5.5)
-        guard #available(macOS 12, iOS 15, tvOS 15, watchOS 8, *) else {
+        #if swift(>=5.5) && canImport(_Concurrency)
+        guard #available(macOS 10.15, iOS 13.0, watchOS 6.0, tvOS 13.0, *) else {
             throw XCTSkip("Task locals are not supported on this platform.")
         }