Rename Matrix.API.set_user_presence to set_presence

This is to keep consistency

src/matrix-api.vala

@@ -194,7 +194,7 @@ public interface Matrix.API : GLib.Object {
      * @param status_message a status message attached to this state
      */
     public abstract void
-    set_user_presence([CCode (delegate_target_pos = 1.5, scope = "async")]
+    set_presence([CCode (delegate_target_pos = 1.5, scope = "async")]
                       owned Matrix.API.Callback? @callback,
                       string user_id,
                       Matrix.Presence presence,

src/matrix-http-api.vala

@@ -617,7 +617,7 @@ public class Matrix.HTTPAPI : GLib.Object, Matrix.API {
     }
 
     public void
-    set_user_presence(API.Callback? cb,
+    set_presence(API.Callback? cb,
                       string user_id,
                       Presence presence,
                       string? status_message)