Editorial: Tweak the return of SetDefaultGlobalBindings (tc39#3139)

In the status quo, the value returned by SetDefaultGlobalBindings
is always just the [[GlobalObject]] of the Realm Record passed in.

At the only invocation of SetDefaultGlobalBindings
(in InitializeHostDefinedRealm),
this is `_realm_.[[GlobalObject]]`, which is just `_global_`.
So use `_global_` instead of `_globalObj_`
(the alias for the value returned by SetDefaultGlobalBindings),
and tweak SetDefaultGlobalBindings to return ~unused~.

spec.html

@@ -11622,8 +11622,8 @@ <h1>InitializeHostDefinedRealm ( ): either a normal completion containing ~unuse
           1. Let _thisValue_ be _global_.
         1. Set _realm_.[[GlobalObject]] to _global_.
         1. Set _realm_.[[GlobalEnv]] to NewGlobalEnvironment(_global_, _thisValue_).
-        1. Let _globalObj_ be ? SetDefaultGlobalBindings(_realm_).
-        1. Create any host-defined global object properties on _globalObj_.
+        1. Perform ? SetDefaultGlobalBindings(_realm_).
+        1. Create any host-defined global object properties on _global_.
         1. Return ~unused~.
       </emu-alg>
     </emu-clause>
@@ -11648,7 +11648,7 @@ <h1>
       <h1>
         SetDefaultGlobalBindings (
           _realmRec_: a Realm Record,
-        ): either a normal completion containing an Object or a throw completion
+        ): either a normal completion containing ~unused~ or a throw completion
       </h1>
       <dl class="header">
       </dl>
@@ -11658,7 +11658,7 @@ <h1>
           1. Let _name_ be the String value of the property name.
           1. Let _desc_ be the fully populated data Property Descriptor for the property, containing the specified attributes for the property. For properties listed in <emu-xref href="#sec-function-properties-of-the-global-object"></emu-xref>, <emu-xref href="#sec-constructor-properties-of-the-global-object"></emu-xref>, or <emu-xref href="#sec-other-properties-of-the-global-object"></emu-xref> the value of the [[Value]] attribute is the corresponding intrinsic object from _realmRec_.
           1. Perform ? DefinePropertyOrThrow(_global_, _name_, _desc_).
-        1. Return _global_.
+        1. Return ~unused~.
       </emu-alg>
     </emu-clause>
   </emu-clause>