Remove a TODO for a closed bug

Change-Id: I9c0f30d43eb4dcf33fe3f8ba0995441dec48036d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2128855Reviewed-by: Ken Rockot <rockot@google.com>
Commit-Queue: Oksana Zhuravlova <oksamyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#755014}

mojo/public/cpp/bindings/BUILD.gn

@@ -270,7 +270,6 @@ source_set("struct_traits") {
 }
 
 if (!is_ios) {
-  # TODO(yzshen): crbug.com/617718 Consider moving this into blink.
   component("wtf_support") {
     sources = [
       "array_traits_web_vector.h",