Remove Rakefile from gemspec files list

Author: smasato

solid_queue.gemspec

@@ -19,7 +19,7 @@ Gem::Specification.new do |spec|
   spec.metadata["source_code_uri"] = "https://github.com/rails/solid_queue"
 
   spec.files = Dir.chdir(File.expand_path(__dir__)) do
-    Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "Rakefile", "README.md", "UPGRADING.md"]
+    Dir["{app,config,db,lib}/**/*", "MIT-LICENSE", "README.md", "UPGRADING.md"]
   end
 
   spec.required_ruby_version = '>= 3.1'