[comments] Drop references to "harmony egal"

It's obsolete, see
https://web.archive.org/web/20161216045840/http://wiki.ecmascript.org/doku.php?id=harmony:egal

Change-Id: I58a7aa8fcf5dff7e76e5603d42aeb53a994c313d
Reviewed-on: https://chromium-review.googlesource.com/c/1278394Reviewed-by: Michael Starzinger <mstarzinger@chromium.org>
Commit-Queue: Marja Hölttä <marja@chromium.org>
Cr-Commit-Position: refs/heads/master@{#56601}

src/objects.h

@@ -1353,7 +1353,7 @@ class Object {
 
   // Checks whether this object has the same value as the given one.  This
   // function is implemented according to ES5, section 9.12 and can be used
-  // to implement the Harmony "egal" function.
+  // to implement the Object.is function.
   V8_EXPORT_PRIVATE bool SameValue(Object* other);
 
   // Checks whether this object has the same value as the given one.