Make SchematicGeneratorSimpleImpl more `protected`

[Rollczi]

https://github.com/Rollczi/LiteCommands/issues/305#issuecomment-1837193724

[huanmeng-qwq]

From my perspective, I want to specify that the name shown to the player should correspond to their language.

// just example
String buildSchematic(SchematicFormat format, SENDER user, Argument<SENDER> argument) {
     String argumentDisplayName = service.getArgumentName(user, argument);
     return format.prefix() + String.format(format.argumentFormat(), argumentDisplayName) + format.suffix();
}