Fix RuboCop config inheritance path in spec/pro

The spec/pro/.rubocop.yml file was trying to inherit from ../.rubocop.yml
which would be spec/.rubocop.yml (doesn't exist).

After the Phase 6 restructuring, spec/pro is two levels deep from the root,
so it needs to inherit from ../../.rubocop.yml to get to the root config.

This fixes the CI error:
Configuration file not found: /home/runner/work/react_on_rails/react_on_rails/spec/.rubocop.yml

Fixes https://github.com/shakacode/react_on_rails/actions/runs/19607768152/job/56149351667

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: justin808

spec/pro/.rubocop.yml

@@ -1,5 +1,5 @@
 inherit_from:
-  - ../.rubocop.yml
+  - ../../.rubocop.yml
 
 Metrics/BlockLength:
   Max: 180