Fix code example showing Streamable usage.

Closes #2391

Author: quaff

src/main/asciidoc/repositories.adoc

@@ -647,10 +647,10 @@ class Product {                                         <1>
   MonetaryAmount getPrice() { … }
 }
 
-@RequiredArgConstructor(staticName = "of")
+@RequiredArgsConstructor(staticName = "of")
 class Products implements Streamable<Product> {         <2>
 
-  private Streamable<Product> streamable;
+  private final Streamable<Product> streamable;
 
   public MonetaryAmount getTotal() {                    <3>
     return streamable.stream()