fix docstring (#36)

Author: raphaelsaavedra

src/link_functions.jl

@@ -24,7 +24,7 @@ function jacobian_link end
 """
     IdentityLink <: Link
 
-Define the map ``\\tilde{f} = f`` where ``\\tilde{f} \\in \\mathbb{R}`` and ``\\tilde{f} \\in \\mathbb{R}``
+Define the map ``\\tilde{f} = f`` where ``f \\in \\mathbb{R}`` and ``\\tilde{f} \\in \\mathbb{R}``
 """
 struct IdentityLink <: Link end
 
@@ -48,4 +48,4 @@ struct LogitLink <: Link end
 const LINKS = [
     IdentityLink;
     LogLink
-]
+]