[ruby/prism] switch unless to if

https://github.com/ruby/prism/commit/29bdbf4212

Co-authored-by: Kevin Newton <kddnewton@gmail.com>

lib/prism/node_ext.rb

@@ -118,7 +118,7 @@ module Prism
         current = current.parent
       end
 
-      unless current.is_a?(ConstantReadNode) || current == nil
+      if !current.is_a?(ConstantReadNode) && !current.nil?
         raise DynamicPartsInConstantPathError, "Constant path contains dynamic parts. Cannot compute full name"
       end