chancloser: use param instead of constant

The param previously was unused so this was likely an oversight or
copy/paste error.
This does not change any behavior, as the method was always called with
the constant previously used. But it makes things more explicit.

lnwallet/chancloser/rbf_coop_test.go

@@ -642,7 +642,7 @@ func (r *rbfCloserTestHarness) assertSingleRbfIteration(
 	// We'll now send in the send offer event, which should trigger 1/2 of
 	// the RBF loop, ending us in the LocalOfferSent state.
 	r.expectHalfSignerIteration(
-		initEvent, balanceAfterClose, absoluteFee, noDustExpect,
+		initEvent, balanceAfterClose, absoluteFee, dustExpect,
 		iteration,
 	)