test: Explain why -whitelist is used in feature_fee_estimation

Also, Remove seemingly unused and undocumented -maxorphantx=1000

test/functional/test_runner.py

@@ -76,7 +76,6 @@ EXTENDED_SCRIPTS = [
 BASE_SCRIPTS = [
     # Scripts that are run by default.
     # Longest test should go first, to favor running tests in parallel
-    'feature_fee_estimation.py',
     'wallet_hd.py',
     'wallet_backup.py',
     # vv Tests less than 5m vv
@@ -110,6 +109,7 @@ BASE_SCRIPTS = [
     'feature_abortnode.py',
     # vv Tests less than 30s vv
     'wallet_keypool_topup.py',
+    'feature_fee_estimation.py',
     'interface_zmq.py',
     'interface_bitcoin_cli.py',
     'mempool_resurrect.py',