[grilo-plugins] Adjust tracker3 query documentation

[Victor Toso <victortoso src gnome org>]

commit 346696c16d48a4503c02a9910065f1659f29310e
Author: Pekka Vuorela <pekka vuorela jolla com>
Date:   Wed May 5 15:45:45 2021 +0300

    Adjust tracker3 query documentation
    
    Commit d3e3b2fd474c switch from string to grilo media type,
    thus adjust the comment here. The example listing
    could be enhanced more but for starters switched nie:url to
    nie:isStoredAs which works with tracker:Audio.

 src/tracker3/grl-tracker-source-api.c | 42 +++--------------------------------
 1 file changed, 3 insertions(+), 39 deletions(-)
---
diff --git a/src/tracker3/grl-tracker-source-api.c b/src/tracker3/grl-tracker-source-api.c
index 5517f47c..1772ec4e 100644
--- a/src/tracker3/grl-tracker-source-api.c
+++ b/src/tracker3/grl-tracker-source-api.c
@@ -561,51 +561,15 @@ grl_tracker_source_writable_keys (GrlSource *source)
  * Columns must be named with the Grilo key name that the column
  * represent. Unnamed or unknown columns will be ignored.
  *
- * First column must be the media type, and it does not need to be named.  It
- * must match with any value supported in rdf:type() property, or
- * grilo#Container. Types understood are:
- *
- * <itemizedlist>
- *   <listitem>
- *     <para>
- *       <literal>nmm#MusicPiece</literal>
- *     </para>
- *   </listitem>
- *   <listitem>
- *     <para>
- *       <literal>nmm#Video</literal>
- *     </para>
- *   </listitem>
- *   <listitem>
- *     <para>
- *       <literal>nmm#Photo</literal>
- *     </para>
- *   </listitem>
- *   <listitem>
- *     <para>
- *       <literal>nmm#Artist</literal>
- *     </para>
- *   </listitem>
- *   <listitem>
- *     <para>
- *       <literal>nmm#MusicAlbum</literal>
- *     </para>
- *   </listitem>
- *   <listitem>
- *     <para>
- *       <literal>grilo#Container</literal>
- *     </para>
- *   </listitem>
- * </itemizedlist>
- *
+ * First column must be grilo media enum value, and it does not need to be named.
  * An example for searching all songs:
  *
  * <informalexample>
  *   <programlisting>
- *     SELECT rdf:type(?song)
+ *     SELECT 1
  *            ?song            AS ?id
  *            nie:title(?song) AS ?title
- *            nie:url(?song)   AS ?url
+ *            nie:isStoredAs(?song) AS ?url
  *     WHERE { ?song a nmm:MusicPiece }
  *   </programlisting>
  * </informalexample>