Rename AsyncMode -> ConcurrentMode

packages/react-is/src/ReactIs.js

@@ -71,14 +71,19 @@ export const StrictMode = REACT_STRICT_MODE_TYPE;
 
 export {isValidElementType};
 
+let hasWarnedAboutDeprecatedIsAsyncMode = false;
+
 // AsyncMode should be deprecated
 export function isAsyncMode(object: any) {
-  lowPriorityWarning(
-    false,
-    'The ReactIs.isAsyncMode() alias has been deprecated, ' +
-      'and will be removed in React 17+. Update your code to use ' +
-      'ReactIs.isConcurrentMode() instead. It has the exact same API.',
-  );
+  if (!hasWarnedAboutDeprecatedIsAsyncMode) {
+    hasWarnedAboutDeprecatedIsAsyncMode = true;
+    lowPriorityWarning(
+      false,
+      'The ReactIs.isAsyncMode() alias has been deprecated, ' +
+        'and will be removed in React 17+. Update your code to use ' +
+        'ReactIs.isConcurrentMode() instead. It has the exact same API.',
+    );
+  }
   return isConcurrentMode(object);
 }
 export function isConcurrentMode(object: any) {