Disable Tags for Posts

Removes the Tags taxonomy from posts: the Tags menu, the tag box in the editor and the tag column disappear.

Code

add_action( 'init', function () {
    unregister_taxonomy_for_object_type( 'post_tag', 'post' );
}, 20 );

Existing tags stay in the database.

Install WPIDE on your WordPress site (it is free) and open Code Snippets.
Use snippet above adds it from the library in one click. Or copy the code into a new snippet with the same code type.
It is added inactive: review the code and settings, then switch it on.