[unit test flake]: TestRbfCloseClosingNegotiationLocal fails

[guggero]

Occasional failure in unit tests (with cover, run here: https://github.com/lightningnetwork/lnd/actions/runs/13397366371/job/37423165732?pr=9521).

 --- FAIL: TestRbfCloseClosingNegotiationLocal (0.01s)
    --- FAIL: TestRbfCloseClosingNegotiationLocal/send_offer_rbf_iteration_loop (0.01s)
        rbf_coop_test.go:334: no dust field set, expected: no dust
        rbf_coop_test.go:334: no dust field set, expected: no dust
        rbf_coop_test.go:251: unexpected state transition: &{{0xc00027c900 0xc000249440}}
        rbf_coop_test.go:334: no dust field set, expected: no dust
        rbf_coop_test.go:334: no dust field set, expected: no dust

[Roasbeef]

Will look into it!