Improve TextField accessibility

Qt Quick accessibility already picks up the text automatically. Instead
set the name (which is a descriptive element) to the placeholder text
which is more descriptive of the element. Otherwise Orca will read the
text twice.

src/declarativeimports/plasmacomponents/qml/TextField.qml

@@ -385,9 +385,8 @@ FocusScope {
         }
     }
 
-    Accessible.name: text
+    Accessible.name: placeholderText
     Accessible.role: Accessible.EditableText
     Accessible.readOnly: readOnly
     Accessible.passwordEdit: echoMode == TextInput.Password || echoMode === TextInput.PasswordEchoOnEdit
-    Accessible.description: placeholderText
 }