Update docs/_docs/reference/contextual/derivation.md

Co-authored-by: Julien Richard-Foy <julien@richard-foy.fr>

Author: bishabosha

docs/_docs/reference/contextual/derivation.md

@@ -49,7 +49,7 @@ given [...]: TC[ ... DerivingType[...] ... ] = TC.derived
 
 What the derived instance precisely looks like depends on the specifics of `DerivingType` and `TC`, we first examine `TC`:
 
-### `TC` takes 1 parameter
+### `TC` takes 1 parameter `F`
 
 Therefore `TC` is defined as `TC[F[A_1, ..., A_K]]` (`TC[F]` if `K == 0`) for some `F`.
 There are two further cases depending on the kinds of arguments: