SEC-2385: Polish Gradle Spring 4 usage doc

docs/manual/src/asciidoc/index.adoc

@@ -285,7 +285,7 @@ By default Gradle will use the newest version when resolving transitive versions
 configurations.all {
     resolutionStrategy.eachDependency { DependencyResolveDetails details ->
         if (details.requested.group == 'org.springframework') {
-            details.useVersion {spring4-version}
+            details.useVersion '{spring4-version}'
         }
     }
 }