[basic.fundamental] Delete repeated cross reference.

We don't seem to make any cross reference more than once per
subclause. We can revisit this policy, but for now the change
makes the text more consistent in this regard.

Author: tkoeppe

source/basic.tex

@@ -5611,7 +5611,7 @@
 \item a variable\iref{basic.pre},
 \item a structured binding\iref{dcl.struct.bind},
 \item a function\iref{dcl.fct},
-\item a function parameter\iref{dcl.fct},
+\item a function parameter,
 \item an enumerator\iref{dcl.enum},
 \item an annotation\iref{dcl.attr.grammar},
 \item a type alias\iref{dcl.typedef},