/*Disable Plugin Installation*/
function restrict_plugin_installation() {
    $roles = wp_roles()->roles;
    foreach ($roles as $role_name => $role_info) {
        $role = get_role($role_name);
        if ($role !== null) {
            $role->remove_cap('install_plugins');
        }
    }
}
add_action('admin_init', 'restrict_plugin_installation');

------------------------------------------

/*Enable Plugin Installation */
function restrict_plugin_installation() {
    $roles = wp_roles()->roles;
    foreach ($roles as $role_name => $role_info) {
        $role = get_role($role_name);
        if ($role !== null) {
            $role->remove_cap('install_plugins');
        }
    }

    $administrator_role = get_role('administrator');
    if ($administrator_role !== null) {
        $administrator_role->add_cap('install_plugins');
    }
}
add_action('admin_init', 'restrict_plugin_installation');