Editorial: Simplify IsFooDescriptor ops

i.e., IsAccessorDescriptor, IsDataDescriptor, IsGenericDescriptor

- Prefer "has a field" over "does not have a field".
- Prefer simple conditions over conjunctions.

spec.html

@@ -4289,8 +4289,9 @@ <h1>
         </dl>
         <emu-alg>
           1. If _Desc_ is *undefined*, return *false*.
-          1. If _Desc_ does not have a [[Get]] field and _Desc_ does not have a [[Set]] field, return *false*.
-          1. Return *true*.
+          1. If _Desc_ has a [[Get]] field, return *true*.
+          1. If _Desc_ has a [[Set]] field, return *true*.
+          1. Return *false*.
         </emu-alg>
       </emu-clause>
 
@@ -4304,8 +4305,9 @@ <h1>
         </dl>
         <emu-alg>
           1. If _Desc_ is *undefined*, return *false*.
-          1. If _Desc_ does not have a [[Value]] field and _Desc_ does not have a [[Writable]] field, return *false*.
-          1. Return *true*.
+          1. If _Desc_ has a [[Value]] field, return *true*.
+          1. If _Desc_ has a [[Writable]] field, return *true*.
+          1. Return *false*.
         </emu-alg>
       </emu-clause>
 
@@ -4319,8 +4321,9 @@ <h1>
         </dl>
         <emu-alg>
           1. If _Desc_ is *undefined*, return *false*.
-          1. If IsAccessorDescriptor(_Desc_) and IsDataDescriptor(_Desc_) are both *false*, return *true*.
-          1. Return *false*.
+          1. If IsAccessorDescriptor(_Desc_) is *true*, return *false*.
+          1. If IsDataDescriptor(_Desc_) is *true*, return *false*.
+          1. Return *true*.
         </emu-alg>
       </emu-clause>