Update proposals/NNNN-parameter-packs.md

Co-authored-by: Becca Royal-Gordon <[email protected]>

Author: hborla

proposals/NNNN-parameter-packs.md

@@ -250,7 +250,7 @@ U := {Float, Double, Character}
 Then the substituted return type becomes a pair of function types:
 
 ```swift
-((Int) -> (Float, Double, Character), (String) -> (Float, Double, Character)>
+((Int) -> (Float, Double, Character), (String) -> (Float, Double, Character))
 ```
 
 Note that the entire replacement type pack for `U` was flattened in each repetition of the pattern type; we did not expand "across" `U`.