Revert of Suppression for valgrind bug (patchset #1 id:1 of https://codereview.chromium.org/1410953002/ )

Reason for revert:
We believe this was suppressing an out of date error that was being triggered because the valgrind bot was not rebuilding nanobench. The valgrind bot has been fixed (is there a bug tracking that?), so this suppression is probably not necessary.

Original issue's description:
> Suppression for valgrind bug
>
> TBR=msarett@google.com
> NOPRESUBMIT=true
> NOTREECHECKS=true
> NOTRY=true
>
> BUG=skia:4478
>
> Committed: https://skia.googlesource.com/skia/+/82e341ff8764ef6168a0c9322089c391d657ae7f

TBR=msarett@google.com
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:4478

Review URL: https://codereview.chromium.org/1406333006

tools/valgrind.supp

@@ -236,15 +236,3 @@
     Memcheck:Addr2
     fun:_ZN22GrAAConvexPathRenderer10onDrawPathERK6SkPathRK11SkStrokeRecP12GrDrawTargetb
 }
-#FIXME (scroggo). skbug.com/4478
-{
-   subset_translate_bench_skbug_4478
-   Memcheck:Leak
-   match-leak-kinds: definite
-   fun:_Znwm
-   fun:_ZN20SubsetTranslateBench6onDrawEiP8SkCanvas
-   fun:_ZN9Benchmark4drawEiP8SkCanvas
-   fun:_ZL4timeiP9BenchmarkP6Target
-   fun:_Z14nanobench_mainv
-   fun:main
-}