Fix Sidekiq::Job::Setter#at type

The top-level `float` alias is deprecated in RBS 4. Use `_ToF`, which
preserves the accepted argument type without producing a validation warning.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: akitoshiga

gems/sidekiq/7.0/job.rbs

@@ -73,7 +73,7 @@ module Sidekiq
 
       private
 
-      def at: (float interval) -> self
+      def at: (_ToF interval) -> self
 
       def initialize: (singleton(Client) klass, Hash[Symbol | string, untyped] opts) -> void
     end