Make @Module @Documented

@ProducerModule is already @Documented

RELNOTES=n/a

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=232902222
diff --git a/java/dagger/Module.java b/java/dagger/Module.java
index 862be7a..bd32a1f 100644
--- a/java/dagger/Module.java
+++ b/java/dagger/Module.java
@@ -17,6 +17,7 @@
 package dagger;
 
 import dagger.internal.Beta;
+import java.lang.annotation.Documented;
 import java.lang.annotation.ElementType;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
@@ -25,6 +26,7 @@
 /**
  * Annotates a class that contributes to the object graph.
  */
+@Documented
 @Retention(RetentionPolicy.RUNTIME)
 @Target(ElementType.TYPE)
 public @interface Module {