Fix <ReferenceInput> throws a recoverable error in production

## Problem

Since #9637, users see an error in production while the app isn't broken

## Solution

Only throw in development.

packages/ra-ui-materialui/src/input/ReferenceInput.tsx

@@ -84,14 +84,11 @@ export const ReferenceInput = (props: ReferenceInputProps) => {
         filter,
     });
 
-    if (props.validate) {
+    if (props.validate && process.env.NODE_ENV !== 'production') {
         throw new Error(
             '<ReferenceInput> does not accept a validate prop. Set the validate prop on the child instead.'
         );
     }
-    if (Children.count(children) !== 1) {
-        throw new Error('<ReferenceInput> only accepts a single child');
-    }
 
     return (
         <ResourceContextProvider value={reference}>