Remove comment discussing non-existent ARRAYSIZE_UNSAFE macro

R=jochen@chromium.org

Review-Url: https://codereview.chromium.org/2282043002
Cr-Commit-Position: refs/heads/master@{#38956}

src/base/macros.h

@@ -21,12 +21,6 @@
 // The expression is a compile-time constant, and therefore can be
 // used in defining new arrays, for example.  If you use arraysize on
 // a pointer by mistake, you will get a compile-time error.
-//
-// One caveat is that arraysize() doesn't accept any array of an
-// anonymous type or a type defined inside a function.  In these rare
-// cases, you have to use the unsafe ARRAYSIZE_UNSAFE() macro below.  This is
-// due to a limitation in C++'s template system.  The limitation might
-// eventually be removed, but it hasn't happened yet.
 #define arraysize(array) (sizeof(ArraySizeHelper(array)))