Fix tests under Ruby 3+

In Ruby 3, you must explicitly use the double splat operator (`**`) to
convert a Hash into keyword arguments. Without it, the Hash is treated
as a single positional argument.

spec/icasework/document_spec.rb

@@ -47,7 +47,7 @@
   end
 
   describe '#find' do
-    subject(:document) { described_class.find(payload) }
+    subject(:document) { described_class.find(**payload) }
 
     before do
       allow(described_class).to receive(:where).and_return(