update valgrind suppressions for revised keepalive thread

Change-Id: I28cc5923866be789d33f4a5f6c0a3be67bf096c3
Reviewed-on: https://skia-review.googlesource.com/65500
Reviewed-by: Mike Klein <mtklein@chromium.org>
diff --git a/tools/valgrind.supp b/tools/valgrind.supp
index 064f8ef..0108b37 100644
--- a/tools/valgrind.supp
+++ b/tools/valgrind.supp
@@ -6,7 +6,7 @@
    Memcheck:Leak
    match-leak-kinds: possible,definite
    ...
-   fun:_ZN8SkThreadC1EPFvPvES0_
+   fun:start_keepalive
    ...
    fun:main
    ...