Skip Pro validation for example app RSpec tests

Example apps are generated with the base gem but run in a monorepo
environment where the Pro gem is available. When RSpec loads the Rails
environment, the version checker detects Pro gem is available but
example app only has 'react-on-rails' npm package, causing validation
to fail.

Solution:
- Add REACT_ON_RAILS_SKIP_VALIDATION=true to run_tests_in() call for
  example apps in run_rspec.rake
- This complements the previous fix for generate_packs in
  shakapacker_examples.rake

This is safe because:
- Example apps are for testing the generator, not production use
- The validation is still enforced in normal app initialization
- It's consistent with skipping validation during generation

Fixes RSpec test failures in Phase 6 monorepo examples CI.

Author: justin808

rakelib/run_rspec.rake

@@ -81,7 +81,8 @@ namespace :run_rspec do
     puts "Creating #{example_type.rspec_task_name} task"
     desc "Runs RSpec for #{example_type.name_pretty} only"
     task example_type.rspec_task_name_short => example_type.gen_task_name do
-      run_tests_in(File.join(examples_dir, example_type.name)) # have to use relative path
+      # Skip validation since example apps only have base gem but Pro may be available in parent bundle
+      run_tests_in(File.join(examples_dir, example_type.name), env_vars: "REACT_ON_RAILS_SKIP_VALIDATION=true")
     end
   end