Fix trivial error in comment

BUG=none
TEST=none
TBR=dcheng

Change-Id: I1393d84231c1693756cb571661ff0d1fda5259da
Reviewed-on: https://chromium-review.googlesource.com/923401
Commit-Queue: Peter Kasting <pkasting@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Peter Kasting <pkasting@chromium.org>
Cr-Commit-Position: refs/heads/master@{#537171}

base/no_destructor.h

@@ -30,7 +30,7 @@ namespace base {
 //     std::string s(16);
 //     crypto::RandString(s.data(), s.size());
 //     return s;
-//   })());
+//   }());
 //   return *nonce;
 // }
 //