fix DebugReducer (#2115)

@_docmentation is available in 5.8 and later

Author: hj56775

Sources/ComposableArchitecture/Reducer/Reducers/DebugReducer.swift

@@ -1,5 +1,5 @@
 extension ReducerProtocol {
-  #if swift(>=5.7)
+  #if swift(>=5.8)
     /// Enhances a reducer with debug logging of received actions and state mutations for the given
     /// printer.
     ///