Update maven.adoc

fixed spelling error in maven part

src/docs/asciidoc/jme3/maven.adoc

@@ -191,7 +191,7 @@ dependencies {
       <scope>runtime</scope>
     </dependency>
     <dependency>
-      <groupId>${jm3_g}</groupId>
+      <groupId>${jme3_g}</groupId>
       <artifactId>jme3-lwjgl</artifactId>
       <version>${jme3_v}</version>
       <scope>runtime</scope>