chore: remove feature guard for token exchange

[wangsijie]

Summary

Remove feature guard for token exchange (impersonation).

Testing

Existing tests should pass.

Checklist

• [ ] .changeset
• [ ] unit tests
• [ ] integration tests
• [ ] necessary TSDoc comments

[github-actions[bot]]

COMPARE TO master

Total Size Diff :chart_with_downwards_trend: -428 Bytes

Diff by File

|Name|Diff| |---|---| |packages/console/src/pages/CustomizeJwtDetails/MainContent/SettingsSection/InstructionTab/index.tsx|:chart_with_downwards_trend: -77 Bytes| |packages/core/src/routes/subject-token.openapi.json|:chart_with_downwards_trend: -31 Bytes| |packages/core/src/routes/subject-token.ts|:chart_with_downwards_trend: -110 Bytes| |packages/core/src/routes/swagger/index.ts|:chart_with_downwards_trend: -60 Bytes| |packages/integration-tests/src/tests/api/oidc/token-exchange.test.ts|:chart_with_downwards_trend: -60 Bytes| |packages/integration-tests/src/tests/api/security.test.ts|:chart_with_downwards_trend: -90 Bytes|