add 0.21 settings changes

[jlopp]

https://lists.linuxfoundation.org/pipermail/bitcoin-core-dev/2021-January/000097.html

$ ./bitcoin-0.20.1/bin/bitcoind --help --help-debug|grep "^ -" | sort > ./options-0.20.txt
$ ./bitcoin-0.21.0/bin/bitcoind --help --help-debug|grep "^ -" | sort > ./options-0.21.txt

$ diff -du ./options-0.20.txt ./options-0.21.txt
--- ./options-0.20.txt	2021-01-17 09:20:05.208319054 -0500
+++ ./options-0.21.txt	2021-01-17 09:20:16.608354065 -0500
@@ -7,9 +7,8 @@
-  -banscore=<n>
-  -bind=<addr>
+  -bind=<addr>[:<port>][=onion]
+  -maxapsfee=<n>
+  -networkactive
+  -peerblockfilters
-  -salvagewallet
+  -settings=<file>
+  -signet
+  -signetchallenge
+  -signetseednode
+  -startupnotify=<cmd>
-  -upgradewallet
-  -zapwallettxes=<mode>
+  -zmqpubsequence=<address>
+  -zmqpubsequencehwm=<n>