[pango] tests: Add an explanation

[Matthias Clasen <matthiasc src gnome org>]

commit 7abe91c208ce7f0c1f6e6c4b13df4de7a664ffa5
Author: Matthias Clasen <mclasen redhat com>
Date:   Tue Jun 9 11:51:45 2020 -0400

    tests: Add an explanation
    
    Lets explain what this test is about, since it doesn't
    appear to test anything.

 tests/testmisc.c | 3 +++
 1 file changed, 3 insertions(+)
---
diff --git a/tests/testmisc.c b/tests/testmisc.c
index 3e629f24..a078944d 100644
--- a/tests/testmisc.c
+++ b/tests/testmisc.c
@@ -23,6 +23,9 @@
 #include <glib.h>
 #include <pango/pangocairo.h>
 
+/* test that we don't crash in shape_tab when the layout
+ * is such that we don't have effective attributes
+ */
 static void
 test_shape_tab_crash (void)
 {