How to hide plugin options for editors via functions.php

This should be easiest way, just add the line to wp-config.php, this will disable plugin and theme editor, both.
define('DISALLOW_FILE_EDIT',true);

If you want to add codes into theme’s function, the code should work for you.

function ra_block_tp_edit( $caps, $cap ) {
    if($cap == 'edit_plugins' )
        $caps[] = 'do_not_allow';
    return $caps;
}
add_filter( 'map_meta_cap', 'ra_block_tp_edit', 10, 3 );

Best of luck.