[mutter] cogl: Remove declaration for long gone function

[Georges Basile Stavracas Neto <gbsneto src gnome org>]

commit 30964051fe748e37bacb482e170d5858b943558d
Author: Jonas Ådahl <jadahl gmail com>
Date:   Fri Nov 22 16:32:16 2019 +0100

    cogl: Remove declaration for long gone function
    
    It was removed in 2011, but the declaration lingered. Until now.
    
    https://gitlab.gnome.org/GNOME/mutter/merge_requests/935

 cogl/cogl/cogl-private.h | 3 ---
 1 file changed, 3 deletions(-)
---
diff --git a/cogl/cogl/cogl-private.h b/cogl/cogl/cogl-private.h
index 12e16233b..42364c720 100644
--- a/cogl/cogl/cogl-private.h
+++ b/cogl/cogl/cogl-private.h
@@ -94,9 +94,6 @@ _cogl_transform_point (const CoglMatrix *matrix_mv,
 gboolean
 _cogl_check_extension (const char *name, char * const *ext);
 
-void
-_cogl_clear (const CoglColor *color, unsigned long buffers);
-
 void
 _cogl_init (void);