Remove un-necessary dependency from parser-doxia-module (#777)

Author: abelsromero

asciidoctor-parser-doxia-module/pom.xml

@@ -43,11 +43,6 @@
             <artifactId>doxia-core</artifactId>
             <version>${doxia.version}</version>
         </dependency>
-        <dependency>
-            <groupId>org.apache.maven.doxia</groupId>
-            <artifactId>doxia-module-markdown</artifactId>
-            <version>${doxia.version}</version>
-        </dependency>
         <dependency>
             <groupId>org.apache.maven.doxia</groupId>
             <artifactId>doxia-site-renderer</artifactId>