I would advice against this. There may be other code in the theme, or javascript, that depends on this option. If you set this to false, you are basically saying that your store does not use stock management at all (which is not true, I believe, otherwise you would turn this off in back office settings page). This can cause you a lot of weird bugs in the future.
Since you are already modifying the template, you can simply delete the code that displays this 'in-stock' information.
Alternatively, if you want this to be 'configurable', you can introduce your own variable, like
{assing var='SHOW_IN_STOCK_INFO' value=false}
and then update already existing condition in the template to include this new variable.