LCORE-1253: Exclude proxy tests from default e2e suite

Remove proxy.feature from test_list.txt. The proxy tests restart
Llama Stack with modified configs and need real proxy infrastructure,
which disrupts other e2e tests when run sequentially in CI.

Proxy tests are run separately via:
  uv run behave tests/e2e/features/proxy.feature --no-capture

Author: max-svistunov

tests/e2e/test_list.txt

@@ -20,4 +20,3 @@ features/mcp_servers_api.feature
 features/mcp_servers_api_auth.feature
 features/mcp_servers_api_no_config.feature
 features/models.feature
-features/proxy.feature