Update FontConfig valgrind suppressions.

tools/valgrind.supp

Index: tools/valgrind.supp
diff --git a/tools/valgrind.supp b/tools/valgrind.supp
index 1f3e6d9ede8cba949503aaa9be7ba9dc6afe0ade..d96ada04e7a374cfc2751f4a37997d9fb5f686f0 100644
--- a/tools/valgrind.supp
+++ b/tools/valgrind.supp
@@ -96,10 +96,20 @@
     font_config_bug_2
     Memcheck:Leak
     fun:*alloc
-    fun:FcPatternObjectInsertElt
+    ...
     fun:Fc*Add*
 }
 {
+    #Same root cause as font_config_bug_2.
+    #The 'leak' here is a copy of rule values, as opposed to new values.
+    font_config_bug_3
+    Memcheck:Leak
+    fun:*alloc
+    fun:FcConfigValues
+    fun:FcConfigSubstituteWithPat
+    fun:FcFontRenderPrepare
+}
+{
     zlib_bug_1
     Memcheck:Cond
     fun:inflateReset2