schema: Add missing mindepth argument to fundchannel

This was likely missed during the zeroconf PR.

Changelog-None

.msggen.json

@@ -390,6 +390,7 @@
             "FundChannel.id": 9,
             "FundChannel.minconf": 10,
             "FundChannel.minconf[]": 4,
+            "FundChannel.mindepth": 12,
             "FundChannel.push_msat": 5,
             "FundChannel.request_amt": 7,
             "FundChannel.utxos[]": 11

doc/schemas/fundchannel.request.json

@@ -40,6 +40,10 @@
       "items": {
         "type": "outpoint"
       }
+    },
+    "mindepth": {
+      "description": "Number of confirmations required before we consider the channel active",
+      "type": "u32"
     }
   }
 }