fix(jans-cli): sample returned by using `--schema` option is malformed for `JansAttribute` schema

[ossdhaval]

As mentioned in #8711, the --schema option (currently) returns a sample of the actual JSON object that the user can use directly to perform operation.

For JansAttribute schema, the sample returned is malformed. It throws an error due to invalid structure of attributeValidation key.

root@jans-node:~# /opt/jans/jans-cli/config-cli.py --schema JansAttribute > /tmp/attribute.json
root@jans-node:~# nano /tmp/attribute.json // Just updated the sample for name key
root@jans-node:~# /opt/jans/jans-cli/config-cli.py --operation-id post-attributes --data /tmp/attribute.json
Server Response:
{
  "server_error": "com.fasterxml.jackson.databind.exc.MismatchedInputException: Cannot deserialize value of type `java.lang.Integer` from Object value (token `JsonToken.START_OBJECT`)\n at [Source: (org.eclipse.jetty.server.HttpInput); line: 1, column: 564] (through reference chain: io.jans.model.JansAttribute["attributeValidation"]->io.jans.model.attribute.AttributeValidation["minLength"])"
}

root@jans-node:~# 

Expectation

Sample should work out of the box.