docs: Remove the "Derived Constraint" argument of `TcPluginSolver` in User's guide
In the user's guide, TcPluginSolver
is defined as follows:
type TcPluginSolver = EvBindsVar -> [Ct] -> [Ct] -> [Ct] -> TcPluginM TcPluginSolveResult
When in fact, the actual definition is this:
type TcPluginSolver = EvBindsVar
-> [Ct] -- ^ Givens
-> [Ct] -- ^ Wanteds
-> TcPluginM TcPluginSolveResult