Update source/expressions.tex

Co-authored-by: Johel Ernesto Guerrero Peña <[email protected]>

Author: Bekenn

source/expressions.tex

@@ -1844,7 +1844,7 @@
 
 \pnum
 A \grammarterm{lambda-expression} is a \defn{lambda}.
-A lambda is a \defn{generic lambda}
+A lambda is \defnx{generic}{lambda!generic}
 if the \grammarterm{parameter-declaration-clause}
 has any generic parameter type placeholders\iref{dcl.spec.auto}, or
 if the lambda has a \grammarterm{template-parameter-list}.