Tweak valgrind suppressions for intentional leaks.

This is a follow up to building the Valgrind bots with GN.

It's not clear why these need to leak, but we might as well
update the suppressions.  The stacks now look like this:

    Memcheck:Leak
    match-leak-kinds: possible
    fun:calloc
    fun:_dl_allocate_tls
    fun:pthread_create@@GLIBC_2.2.5
    fun:_ZN8SkThreadC1EPFvPvES0_
    fun:_Z14nanobench_mainv
    fun:(below main)

We suppress fun:main in that last slot, so just make it ...

TBR=

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search?issue=2347153002

Review-Url: https://codereview.chromium.org/2347153002
diff --git a/tools/valgrind.supp b/tools/valgrind.supp
index 3abf592..1399c3e 100644
--- a/tools/valgrind.supp
+++ b/tools/valgrind.supp
@@ -9,7 +9,7 @@
    fun:_ZN8SkThreadC1EPFvPvES0_
    ...
    fun:_Z7dm_mainv
-   fun:main
+   ...
 }
 
 # Intentional thread / memory leak in nanobench.
@@ -21,7 +21,7 @@
    fun:_ZN8SkThreadC1EPFvPvES0_
    ...
    fun:_Z14nanobench_mainv
-   fun:main
+   ...
 }
 
 # Third party lib, driver issues.