Update docs to use case key paths

Author: stephencelis

Sources/ComposableArchitecture/Documentation.docc/Tutorials/MeetTheComposableArchitecture/02-Navigation/04-NavigationStacks/02-04-02-code-0003.swift

@@ -2,7 +2,7 @@ struct ContactsView: View {
   let store: StoreOf<ContactsFeature>
 
   var body: some View {
-    NavigationStackStore(self.store.scope(state: \.path, action: { .path($0) })) {
+    NavigationStackStore(self.store.scope(state: \.path, action: \.path)) {
       WithViewStore(self.store, observe: \.contacts) { viewStore in
         List {
           ForEach(viewStore.state) { contact in

Sources/ComposableArchitecture/Documentation.docc/Tutorials/MeetTheComposableArchitecture/02-Navigation/04-NavigationStacks/02-04-02-code-0004.swift

@@ -2,7 +2,7 @@ struct ContactsView: View {
   let store: StoreOf<ContactsFeature>
 
   var body: some View {
-    NavigationStackStore(self.store.scope(state: \.path, action: { .path($0) })) {
+    NavigationStackStore(self.store.scope(state: \.path, action: \.path)) {
       WithViewStore(self.store, observe: \.contacts) { viewStore in
         List {
           ForEach(viewStore.state) { contact in

Sources/ComposableArchitecture/Documentation.docc/Tutorials/MeetTheComposableArchitecture/02-Navigation/04-NavigationStacks/02-04-02-code-0005-previous.swift

@@ -2,7 +2,7 @@ struct ContactsView: View {
   let store: StoreOf<ContactsFeature>
 
   var body: some View {
-    NavigationStackStore(self.store.scope(state: \.path, action: { .path($0) })) {
+    NavigationStackStore(self.store.scope(state: \.path, action: \.path)) {
       WithViewStore(self.store, observe: \.contacts) { viewStore in
         List {
           ForEach(viewStore.state) { contact in

Sources/ComposableArchitecture/Documentation.docc/Tutorials/MeetTheComposableArchitecture/02-Navigation/04-NavigationStacks/02-04-02-code-0005.swift

@@ -2,7 +2,7 @@ struct ContactsView: View {
   let store: StoreOf<ContactsFeature>
 
   var body: some View {
-    NavigationStackStore(self.store.scope(state: \.path, action: { .path($0) })) {
+    NavigationStackStore(self.store.scope(state: \.path, action: \.path)) {
       WithViewStore(self.store, observe: \.contacts) { viewStore in
         List {
           ForEach(viewStore.state) { contact in

Sources/ComposableArchitecture/UIKit/IfLetUIKit.swift

@@ -20,7 +20,7 @@ extension Store {
   ///   func viewDidLoad() {
   ///     // ...
   ///     self.store
-  ///       .scope(state: \.optionalChild, action: { .child($0) })
+  ///       .scope(state: \.optionalChild, action: \.child)
   ///       .ifLet(
   ///         then: { [weak self] childStore in
   ///           self?.navigationController?.pushViewController(