[class.cdtor] Remove duplicate UB labels

Author: jensmaurer

source/classes.tex

@@ -6105,7 +6105,7 @@
 or base class of the object before the constructor begins execution results in
 undefined behavior\ubdef{class.cdtor.before.ctor.after.dtor}. For an object with a non-trivial destructor, referring to
 any non-static member or base class of the object after the destructor finishes
-execution results in undefined behavior\ubdef{class.cdtor.before.ctor.after.dtor}.
+execution results in undefined behavior.
 \begin{example}
 \begin{codeblock}
 struct X { int i; };
@@ -6190,7 +6190,7 @@
 indirectly derive from
 \tcode{B}
 shall have started and the destruction of these classes shall not have
-completed, otherwise the conversion results in undefined behavior\ubdef{class.cdtor.convert.or.form.pointer}.
+completed, otherwise the conversion results in undefined behavior.
 To form a pointer to (or access the value of) a direct non-static member of
 an object
 \tcode{obj},