[gtk+] Remove a duplicate doc comment

[Matthias Clasen <matthiasc src gnome org>]

commit 6c33e37db2e9b1b8089c6580bdfecbbbcc56c46c
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Dec 26 19:18:45 2017 -0500

    Remove a duplicate doc comment
    
    g-ir-scanner complains about this.

 gdk/gdkcontentserializer.c |    6 ------
 1 files changed, 0 insertions(+), 6 deletions(-)
---
diff --git a/gdk/gdkcontentserializer.c b/gdk/gdkcontentserializer.c
index ff22678..f0bf750 100644
--- a/gdk/gdkcontentserializer.c
+++ b/gdk/gdkcontentserializer.c
@@ -39,12 +39,6 @@
  * data transfers.
  */
 
-/**
- * GdkContentSerializer:
- *
- * Contains only private fields and should not be directly accessed.
- */
-
 typedef struct _Serializer Serializer;
 
 struct _Serializer