Keep funding confirmed through test reorgs

The test gave funding six confirmations while allowing six-block
reorgs. That drops regular channel funding to zero confirmations and
changes the scenario from a close reorg into a funding force-close.

rust-lightning PR #4231 keeps trusted zero-conf channels open after
funding is reorged out, but regular channels still force-close at zero
confirmations. Mine one extra block so the deepest reorg leaves one
confirmation.

Preserve the CI counterexample that exposed this boundary.

Co-Authored-By: HAL 9000

Author: tnull

tests/reorg_test.proptest-regressions

@@ -0,0 +1 @@
+cc 06354c9b049db51c31557bf46d86a68bdd4049577cbd9190fb81c7824b18f0e6 # shrinks to reorg_depth = 6, force_close = false

tests/reorg_test.rs

@@ -76,7 +76,9 @@ proptest! {
 				nodes_funding_tx.insert(node.node_id(), funding_txo);
 			}
 
-			generate_blocks_and_wait(bitcoind, electrs, 6).await;
+			// Keep funding confirmed across the deepest reorg. rust-lightning PR #4231 exempts
+			// only trusted zero-conf channels; regular channels still force-close at zero confirmations.
+			generate_blocks_and_wait(bitcoind, electrs, 7).await;
 			sync_wallets!();
 
 			reorg!(reorg_depth);