disable tags on wordpress text editor

WordPress already disallows the use of JavaScript in the editor for users without the unfiltered_html capability. By default, only the Administrator and Editor roles have this capability. If necessary, you could remove this capability from Editor users as well. (It doesn’t make sense to remove it from Administrators, because they will still have the ability to install plugins, and thus execute whatever kind of code they want to.)

This code should do that for you:

function wpse_285333_remove_unfiltered_html_cap() {
    $wp_roles = wp_roles();
    $wp_roles->remove_cap( 'editor', 'unfiltered_html' );
}

// This function actually only needs to run once, so you can comment this out
// after loading the site once.
add_action( 'init', 'wpse_285333_remove_unfiltered_html_cap', 5 );

There are also plugins available to help with managing roles and capabilities.