Update material_specification.adoc

Fixed broken link to javadocs.

src/docs/asciidoc/jme3/advanced/material_specification.adoc

@@ -281,7 +281,7 @@ Material MyGrass : Common/MatDefs/Misc/TestMaterial.j3md {
 
 === Java interface for J3M
 
-It is possible to generate an identical J3M file using Java code, by using the classes in the com.jme3.material package. Specifics of the link:http://jmonkeyengine.org/javadoc/com/jme3/material/Material.html[Material API] will not be provided in this document. The J3M file above is represented by this Java code:
+It is possible to generate an identical J3M file using Java code, by using the classes in the com.jme3.material package. Specifics of the link:http://javadoc.jmonkeyengine.org/com/jme3/material/Material.html[Material API] will not be provided in this document. The J3M file above is represented by this Java code:
 
 [source,java]
 ----