[CS] Remove function component constraints

FunctionInput relies on being able to represent
parameter lists as tuples, which won't be possible
once parameter flags are stripped from tuple types.
FunctionResult is reasonable, but is currently
unused.

include/swift/Sema/Constraint.h

@@ -171,12 +171,6 @@ enum class ConstraintKind : char {
   /// The key path type is chosen based on the selection of overloads for the
   /// member references along the path.
   KeyPath,
-  /// The first type is a function type, the second is the function's
-  /// input type.
-  FunctionInput,
-  /// The first type is a function type, the second is the function's
-  /// result type.
-  FunctionResult,
   /// The first type will be equal to the second type, but only when the
   /// second type has been fully determined (and mapped down to a concrete
   /// type). At that point, this constraint will be treated like an `Equal`
@@ -691,8 +685,6 @@ public:
     case ConstraintKind::KeyPath:
     case ConstraintKind::KeyPathApplication:
     case ConstraintKind::Defaultable:
-    case ConstraintKind::FunctionInput:
-    case ConstraintKind::FunctionResult:
       return ConstraintClassification::TypeProperty;
 
     case ConstraintKind::Disjunction: