fix: Remove outdated "Cannot activate" limitation from test expectations

After implementing workflow activation/deactivation operations, the
"Cannot activate" limitation no longer applies. Updated the test to
match the current API capabilities.

Related to #399

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

Co-Authored-By: Claude <noreply@anthropic.com>

Conceived by Romuald Członkowski - www.aiadvisors.pl/en

tests/integration/n8n-api/system/list-tools.test.ts

@@ -101,7 +101,6 @@ describe('Integration: handleListAvailableTools', () => {
 
       // Common known limitations
       const limitationsText = data.limitations.join(' ');
-      expect(limitationsText).toContain('Cannot activate');
       expect(limitationsText).toContain('Cannot execute workflows directly');
     });
   });