Fix couple of uses of $state.value instead of state.

Author: mluisbrown

Sources/ComposableArchitecture/UIKit/IfLetUIKit.swift

@@ -51,7 +51,7 @@ extension Store {
         }
       )
       .startWithValues { store in
-        if store.$state.value == nil { `else`() }
+        if store.state == nil { `else`() }
       }
 
     let unwrapDisposable =

Tests/ComposableArchitectureTests/StoreTests.swift

@@ -239,7 +239,7 @@ final class StoreTests: XCTestCase {
       .ifLet(
         then: { store in
           stores.append(store)
-          outputs.append(store.$state.value)
+          outputs.append(store.state)
         },
         else: {
           outputs.append(nil)