Update position controller package.xml (#1431)

Author: delipl

position_controllers/package.xml

@@ -2,7 +2,7 @@
 <package format="3">
   <name>position_controllers</name>
   <version>4.17.0</version>
-  <description>Generic controller for forwarding commands.</description>
+  <description>Generic position controller for forwarding position commands.</description>
 
   <maintainer email="[email protected]">Bence Magyar</maintainer>
   <maintainer email="[email protected]">Denis Štogl</maintainer>