Tell users to solve lowest-complexity failures first

When failure output is truncated by --max-failures, print an explicit note that
failures are ordered by complexity and the displayed failures should be solved
first. Keep the runner diagnostics test covering the truncation area.

Author: tobi

lib/liquid/spec/cli/runner.rb

@@ -1480,6 +1480,7 @@ def print_failures(failures, max_failures = nil)
             # Show truncation message if we limited output
             if max_failures && sorted_failures.size > max_failures
               puts "\e[2m(... #{sorted_failures.size - max_failures} more failures not shown due to --max-failures #{max_failures} ...)\e[0m"
+              puts "\e[2mFailures are ordered by complexity. Solve above failures first.\e[0m"
               puts ""
             end
           end

test/runner_diagnostics_test.rb

@@ -113,6 +113,7 @@ def test_printed_failures_are_lowest_complexity_across_prioritized_and_suite_spe
       assert_includes stdout, "1) object_string_literal"
       refute_includes stdout, "1) high_added_failure"
       assert_includes stdout, "(... 1 more failures not shown due to --max-failures 1 ...)"
+      assert_includes stdout, "Failures are ordered by complexity. Solve above failures first."
     end
   end
 end