Test should be passing block to RSpec wait_for

Fixes flaky test

spec/integrations/client_zpty_spec.rb

@@ -5,6 +5,6 @@ describe 'a running zpty command' do
     sleep 1 # Give a little time for precmd hooks to run
     session.run_command('zpty -t kitty; echo $?')
 
-    wait_for(session.content).to end_with("\n0")
+    wait_for { session.content }.to end_with("\n0")
   end
 end