[Config] secret should be overrided

For security, `framework.secret ` configuration should not be equals to "ThisTokenIsNotSoSecretChangeIt" (the default value in symfony-standard).

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT