Merge bitcoin/bitcoin#32765: test: Fix list index out of range error in feature_bip68_sequence.py

e285e69 test: Fix list index out of range error in feature_bip68_sequence.py (zaidmstrr)

Pull request description:

  Fixes [#32334](bitcoin/bitcoin#32334)

  The test `feature_bip68_sequence.py` fails with `IndexError: list index out of range` error due to a mismatch between the number of inputs requested (at random) and the number of UTXOs available. The error is reproducible with the randomseed:
  ```
  $ ./build/test/functional/feature_bip68_sequence.py --randomseed 6169832640268785903
  ```
  This PR adds a valid upper bound to randomly select the inputs.

ACKs for top commit:
  maflcko:
    lgtm ACK e285e69
  Prabhat1308:
    re-ACK [`e285e69`](bitcoin/bitcoin@e285e69)
  theStack:
    ACK e285e69

Tree-SHA512: 2e5e19d5db2880915f556ed4444abed94e9ceb1ecee5f857df5616040c850dae682aaa4ade3060c48acb16676df92ba81c3af078c1958965e9e874e7bb489388

Author: fanquake

test/functional/feature_bip68_sequence.py

@@ -144,8 +144,10 @@ def test_sequence_lock_confirmed_inputs(self):
         # between height/time locking). Small random chance of making the locks
         # all pass.
         for _ in range(400):
+            available_utxos = len(utxos)
+
             # Randomly choose up to 10 inputs
-            num_inputs = random.randint(1, 10)
+            num_inputs = random.randint(1, min(10, available_utxos))
             random.shuffle(utxos)
 
             # Track whether any sequence locks used should fail