Bug 1429904 - Remove a comment about std::string. r=njn

nsCString is the idiomatic string class we want to use anyway. There's no need
to think about std::string here.

MozReview-Commit-ID: 1rjZAyqp13d

--HG--
extra : rebase_source : 92c4eb22876c4fc89f00104c56f92a75053284e9

tools/profiler/core/ProfileBufferEntry.h

@@ -170,8 +170,6 @@ public:
   };
 
   struct FrameKey {
-    // This cannot be a std::string, as it is not memmove compatible, which
-    // is used by nsHashTable
     const nsCString mLocation;
     const mozilla::Maybe<unsigned> mLine;
     const mozilla::Maybe<unsigned> mCategory;