Fix GET_FEATURES GMP doc.

Some copy-paste errors in the description are fixed and a missing
pattern element is added.

src/schema_formats/XML/GMP.xml.in

@@ -11168,12 +11168,13 @@ END:VCALENDAR
  <summary>Get a list of optional features</summary>
  <description>
  <p>
- The client uses the get_feeds command to get a list of optional
+ The client uses the get_features command to get a list of optional
  features.
  If the command sent by the client was valid, the manager will
- reply with a list of feeds to the client.
+ reply with a list of features to the client.
  </p>
  </description>
+ <pattern></pattern>
  <response>
  <pattern>
  <attrib>