Correct default output directory in ManualRestDocumentation javadoc

Closes gh-553

spring-restdocs-core/src/main/java/org/springframework/restdocs/ManualRestDocumentation.java

@@ -1,5 +1,5 @@
 /*
- * Copyright 2014-2016 the original author or authors.
+ * Copyright 2014-2018 the original author or authors.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -37,7 +37,7 @@ public final class ManualRestDocumentation implements RestDocumentationContextPr
 
 	/**
 	 * Creates a new {@code ManualRestDocumentation} instance that will generate snippets
-	 * to <gradle/maven build path>/generated-snippet.
+	 * to <gradle/maven build path>/generated-snippets.
 	 */
 	public ManualRestDocumentation() {
 		this(getDefaultOutputDirectory());