Rollup merge of #161367 - Urgau:triagebot-no-merges-upd, r=bjorn3

Reflect current PR title names for subtree syncs in triagebot no-merges

Noticed that the current PR title names for subtree syncs seems to have changed (or at least for some) and is now "Subtree sync" (or it's lower-cased variant).

Let's update the triagebot config so the merge commit handler don't for those expected cases.

- https://github.com/rust-lang/rust/pull/157533#issuecomment-4639219811
- https://github.com/rust-lang/rust/pull/155978#issuecomment-4347647470