Remove apply_transaction helper

[pickfire]

Not sure why there is this TODO, so I cleaned it up.

[the-mikedavis]

Ah I forgot about this TODO: we removed the need for the apply_transaction helper a while ago but didn't want to complicate the diff. I think we're safe to remove it now 👍

There's one more reference of it in the integration test suite helpers to be removed

[pickfire]

There's one more reference of it in the integration test suite helpers to be removed

I can't find it with rg apply_transaction.

[the-mikedavis]

Ah actually looks like there's two of them

helix/helix-term/tests/test/helpers.rs

Line 133 in edd0ba7

helix_view::apply_transaction(&transaction, doc, view);

and

helix/helix-term/tests/test/helpers.rs

Line 318 in edd0ba7

helix_view::apply_transaction(&trans, doc, view);

[pickfire]

Oh, looks like I accidentally added test/ to my git ignore, no wonder.

[the-mikedavis]

Thanks for cleaning this up!