[expr.delete] Remove duplicate UB label

Author: jensmaurer

source/expressions.tex

@@ -6152,7 +6152,7 @@
 element of the array created by that \grammarterm{new-expression}.
 Zero-length arrays do not have a first element.
 \end{footnote}
-If not, the behavior is undefined\ubdef{expr.delete.mismatch}.
+If not, the behavior is undefined.
 \begin{note}
 This means that the syntax of the \grammarterm{delete-expression} must
 match the type of the object allocated by \keyword{new}, not the syntax of the