fix: prevent RSpec 3.5+ from auto-discovering test example groups

Use anonymous classes instead of RSpec::Core::ExampleGroup.describe()
to create example groups for formatter testing. This prevents RSpec 3.5+
from automatically registering and executing these test groups, which
was causing false test failures.

Author: bf4

spec/api_formatter_spec.rb

@@ -2,7 +2,18 @@
 
 describe RspecApiDocumentation::ApiFormatter do
   let(:metadata) { {} }
-  let(:group) { RSpec::Core::ExampleGroup.describe("Orders", metadata) }
+  let(:group) { 
+    # Create an anonymous class that inherits from ExampleGroup but doesn't auto-register
+    Class.new(RSpec::Core::ExampleGroup) do
+      def self.description
+        "Orders"
+      end
+      
+      def self.metadata
+        {}
+      end
+    end
+  }
   let(:output) { StringIO.new }
   let(:formatter) { RspecApiDocumentation::ApiFormatter.new(output) }