[ruby/prism] Remove category keyword from warn call

`category` is only supported from Ruby 3.0 onwards and prism can still run with Ruyb 2.7

https://github.com/ruby/prism/commit/335a193851

lib/prism/node_ext.rb

@@ -9,7 +9,7 @@ module Prism
       location = location[0].label if location
       suggest = replacements.map { |replacement| "#{self.class}##{replacement}" }
 
-      warn(<<~MSG, category: :deprecated)
+      warn(<<~MSG)
         [deprecation]: #{self.class}##{location} is deprecated and will be \
         removed in the next major version. Use #{suggest.join("/")} instead.
         #{(caller(1, 3) || []).join("\n")}