Editorial: Fix grammar in [LegacyNamespace] definition

Also improve the cross-linking. Fixes #1296.

Author: shvaikalesh

index.bs

@@ -10450,8 +10450,8 @@ the [=interface object=] for this interface will not be created as a property of
 object, but rather as a property of the [=namespace=] identified by the argument to the extended
 attribute.
 
-The [{{LegacyNamespace}}] extended attribute [=takes an identifier|take an identifier=].
-This identifier must be the identifier of a namespace.
+The [{{LegacyNamespace}}] extended attribute must [=take an identifier=].
+This identifier must be the [=identifier=] of a [=namespace=] definition.
 
 The [{{LegacyNamespace}}] and [{{LegacyNoInterfaceObject}}]
 extended attributes must not be specified on the same interface.