[ruby/prism] Looks like Symbol#name wasn't a thing in 2.7, so need to switch back to to_s

https://github.com/ruby/prism/commit/0b90c9a398

lib/prism/ripper_compat.rb

@@ -200,7 +200,7 @@ module Prism
     # Visit a RequiredParameterNode.
     def visit_required_parameter_node(node)
       bounds(node.location)
-      on_ident(node.name.name)
+      on_ident(node.name.to_s)
     end
 
     # Visit a BreakNode.