Update RPCs added and removed in 0.20

Author: cornelius

helpers/rpc/annotations-bitcoin-0.21.json

@@ -137,6 +137,9 @@
       ]
     }
   },
+  "dumptxoutset": {
+    "added": "0.20"
+  },
   "dumpwallet": {
     "see_also": {
       "commands": [
@@ -193,6 +196,9 @@
       ]
     }
   },
+  "generatetodescriptor": {
+    "added": "0.20"
+  },
   "getaccount": {
     "removed": "0.18.0"
   },