[Config] Fixed error messages of min/max validation methods

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | 
| License       | MIT
| Doc PR        | 

This PR fixes the error messages of the configuration validation methods `min` and `max`. The error message was "Should be greater/less than: <value>" but should be "Should be greater/less than or equal to <value>".