Preserve required RBI keyword parameters

Author: OskarEichler

lib/rbs/prototype/rbi.rb

@@ -549,10 +549,10 @@ def parse_params(args_node, args, method_type, variables:, overloads:)
         while kw
           name, value = kw.children[0].children
           if (type = vars[name])
-            if value
-              optional_keywords[name] = Types::Function::Param.new(type: type, name: name)
-            else
+            if value.nil? || value == :NODE_SPECIAL_REQUIRED_KEYWORD
               required_keywords[name] = Types::Function::Param.new(type: type, name: name)
+            else
+              optional_keywords[name] = Types::Function::Param.new(type: type, name: name)
             end
           end