[gnumeric] tests: suppress a bitfield assignment in gdkpixbuf.

[Morten Welinder <mortenw src gnome org>]

commit 7f52964f7cf2b91e4a1b7735f0d98eae67e8bf16
Author: Morten Welinder <terra gnome org>
Date:   Mon Mar 8 18:46:20 2021 -0500

    tests: suppress a bitfield assignment in gdkpixbuf.
    
    valgrind doesn't track that right.

 test/common.supp | 6 ++++++
 1 file changed, 6 insertions(+)
---
diff --git a/test/common.supp b/test/common.supp
index aa1d5d9ad..c59ae75c3 100644
--- a/test/common.supp
+++ b/test/common.supp
@@ -956,3 +956,9 @@
    ...
    fun:g_simple_async_result_complete
 }
+
+{
+   gdk_pixbuf_has_alpha_bitfield
+   Memcheck:Cond
+   fun:gdk_pixbuf_add_alpha
+}