fix: update policy description

Author: jgiovaresco

pom.xml

@@ -25,7 +25,7 @@
     <version>2.0.1</version>
 
     <name>Gravitee.io APIM - Policy - Callout HTTP</name>
-    <description>Description of the CalloutHttp Gravitee Policy</description>
+    <description>Invoke an HTTP(S) URL and place a subset or all of the content in one or more variables of the request execution context</description>
 
     <parent>
         <groupId>io.gravitee</groupId>