Removed unused UnresolvedType::get (#5322)

Author: mxswd

include/swift/AST/Types.h

@@ -991,8 +991,6 @@ class UnresolvedType : public TypeBase {
     : TypeBase(TypeKind::Unresolved, &C,
        RecursiveTypeProperties(RecursiveTypeProperties::HasUnresolvedType)) { }
 public:
-  static Type get(const ASTContext &C);
-  
   // Implement isa/cast/dyncast/etc.
   static bool classof(const TypeBase *T) {
     return T->getKind() == TypeKind::Unresolved;