Change 'title' to 'label' in header items (#1504)

Author: christophby

versioned_docs/version-7.x/native-stack-navigator.md

@@ -945,7 +945,7 @@ Example:
 unstable_headerLeftItems: () => [
   {
     type: 'button',
-    title: 'Edit',
+    label: 'Edit',
     onPress: () => {
       // Do something
     },
@@ -989,7 +989,7 @@ Example:
 unstable_headerRightItems: () => [
   {
     type: 'button',
-    title: 'Edit',
+    label: 'Edit',
     onPress: () => {
       // Do something
     },