[DependencyInjection] Remove TaggedIterator and TaggedLocator attributes

[javiereguiluz]

Fixes #21098.

In service_container/tags.rst there are some occurrences of a similar but different class:

use Symfony\Component\DependencyInjection\Argument\TaggedIteratorArgument;

It's needed because i's used by the tagged_iterator() method (which is not deprecated).

[GromNaN]

In service_container/tags.rst there are some occurrences of a similar but different class:

use Symfony\Component\DependencyInjection\Argument\TaggedIteratorArgument;

It's needed because it's used by the tagged_iterator() method (which is not deprecated).

I think it's fine to remove it as the class is not actually used in the code example.

It seems you haven't seen my PR: #21100.