Editorial: Remove unnecessary undefined type from property descriptor tests

`Is{Accessor,Data,Generic}Descriptor` are never called with `undefined`.

Author: anba

spec.html

@@ -4411,13 +4411,12 @@ <h1>The Property Descriptor Specification Type</h1>
       <emu-clause id="sec-isaccessordescriptor" type="abstract operation">
         <h1>
           IsAccessorDescriptor (
-            _Desc_: a Property Descriptor or *undefined*,
+            _Desc_: a Property Descriptor,
           ): a Boolean
         </h1>
         <dl class="header">
         </dl>
         <emu-alg>
-          1. If _Desc_ is *undefined*, return *false*.
           1. If _Desc_ has a [[Get]] field, return *true*.
           1. If _Desc_ has a [[Set]] field, return *true*.
           1. Return *false*.
@@ -4427,13 +4426,12 @@ <h1>
       <emu-clause id="sec-isdatadescriptor" type="abstract operation">
         <h1>
           IsDataDescriptor (
-            _Desc_: a Property Descriptor or *undefined*,
+            _Desc_: a Property Descriptor,
           ): a Boolean
         </h1>
         <dl class="header">
         </dl>
         <emu-alg>
-          1. If _Desc_ is *undefined*, return *false*.
           1. If _Desc_ has a [[Value]] field, return *true*.
           1. If _Desc_ has a [[Writable]] field, return *true*.
           1. Return *false*.
@@ -4443,13 +4441,12 @@ <h1>
       <emu-clause id="sec-isgenericdescriptor" type="abstract operation">
         <h1>
           IsGenericDescriptor (
-            _Desc_: a Property Descriptor or *undefined*,
+            _Desc_: a Property Descriptor,
           ): a Boolean
         </h1>
         <dl class="header">
         </dl>
         <emu-alg>
-          1. If _Desc_ is *undefined*, return *false*.
           1. If IsAccessorDescriptor(_Desc_) is *true*, return *false*.
           1. If IsDataDescriptor(_Desc_) is *true*, return *false*.
           1. Return *true*.