Don't generate documentation on test

Author: KitaitiMakoto

bindings/ruby/tests/test_package.rb

@@ -23,7 +23,7 @@ def test_install
       version = match_data[2]
       basename = "whisper.#{RbConfig::CONFIG["DLEXT"]}"
       Dir.mktmpdir do |dir|
-        system "gem", "install", "--install-dir", dir.shellescape, "pkg/#{filename.shellescape}", exception: true
+        system "gem", "install", "--install-dir", dir.shellescape, "--no-document", "pkg/#{filename.shellescape}", exception: true
         assert_path_exist File.join(dir, "gems/whispercpp-#{version}/lib", basename)
       end
     end