CwFs: grammatical error (last small commit today, I promise)

src/CwF.lagda.md

@@ -55,7 +55,7 @@ record is-CwF {o h f : _} (𝓒 : Precategory o h) : Type (lsuc (o ⊔ h ⊔ f))
     𝓕 : Functor (𝓒 ^op) (Fams f)
 ```
 
-Two functions, $Ty$ and $Tm$ are defined in terms of $\mathcal F$, giving a contexts set of syntactic types, and terms respectively.
+Two functions, $Ty$ and $Tm$ are defined in terms of $\mathcal F$, giving a context's set of syntactic types, and terms respectively.
 ```
   open Precategory 𝓒
   open Functor 𝓕