Changed warning wording slightly

Author: bvaughn

packages/react/src/__tests__/useRef-test.internal.js

@@ -161,13 +161,13 @@ describe('useRef', () => {
 
   it('should error if not provided a callback', () => {
     expect(() => React.useRef(undefined)).toWarnDev(
-      'useRef requires a render prop but was given undefined.',
+      'useRef requires a render function but was given undefined.',
     );
     expect(() => React.useRef(null)).toWarnDev(
-      'useRef requires a render prop but was given null.',
+      'useRef requires a render function but was given null.',
     );
     expect(() => React.useRef('foo')).toWarnDev(
-      'useRef requires a render prop but was given string.',
+      'useRef requires a render function but was given string.',
     );
   });
 });

packages/react/src/useRef.js

@@ -14,7 +14,7 @@ export default function useRef<Props, ElementType: React$ElementType>(
 ) {
   warning(
     typeof renderProp === 'function',
-    'useRef requires a render prop but was given %s.',
+    'useRef requires a render function but was given %s.',
     renderProp === null ? 'null' : typeof renderProp,
   );