[DependencyInjection] Fix parameter description in ConfigurationExtensionInterface

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #10845
| License       | MIT
| Doc PR        | none

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | #10845
| License       | MIT
| Doc PR        | none

This fixes the description of parameter `array $config` in file ConfigurationExtensionInterface.php by removing the extra `$config`.