buffer: remove obsolete and confusing comment

This comment applied to a line that was removed in
dd67608bfd
and is no longer relevant.

PR-URL: https://github.com/nodejs/node/pull/7264
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

lib/buffer.js

@@ -212,9 +212,6 @@ function allocate(size) {
     alignPool();
     return b;
   } else {
-    // Even though this is checked above, the conditional is a safety net and
-    // sanity check to prevent any subsequent typed array allocation from not
-    // being zero filled.
     return createUnsafeBuffer(size);
   }
 }