Fix version

Author: sea-bass

example_external/package.xml

@@ -2,7 +2,7 @@
 <?xml-model href="http://download.ros.org/schema/package_format3.xsd" schematypens="http://www.w3.org/2001/XMLSchema"?>
 <package format="3">
   <name>generate_parameter_library_example_external</name>
-  <version>0.4.0</version>
+  <version>0.3.9</version>
   <description>Example usage of a parameter header generated in another package.</description>
   <maintainer email="[email protected]">Paul Gesel</maintainer>
   <license>BSD-3-Clause</license>