Set GraphQL cache regardless of bootsnap

The cache has nothing to do with bootsnap, so we don't need to piggyback
off of it at all. This will prevent bootsnap cache to be polluted by the
graphql gem, and allow more apps to leverage GQL caching.

lib/graphql/railtie.rb

@@ -2,12 +2,7 @@
 module GraphQL
   class Railtie < Rails::Railtie
     config.before_configuration do
-      # Bootsnap compile cache has similar expiration properties,
-      # so we assume that if the user has bootsnap setup it's ok
-      # to piggy back on it.
-      if ::Object.const_defined?("Bootsnap::CompileCache::ISeq") && Bootsnap::CompileCache::ISeq.cache_dir
-        Language::Parser.cache ||= Language::Cache.new(Pathname.new(Bootsnap::CompileCache::ISeq.cache_dir).join('graphql'))
-      end
+      Language::Parser.cache ||= Language::Cache.new(Rails.root.join("tmp/graphql"))
     end
   end
 end