Merge #21426: rpc: remove scantxoutset EXPERIMENTAL warning

2f0b25a rpc: remove scantxoutset EXPERIMENTAL warning (Jon Atack)

Pull request description:

  Remove old warning per IRC wallet meeting discussion at http://www.erisian.com.au/bitcoin-core-dev/log-2021-03-12.html#l-467

  This RPC was merged 3 years ago in #12196.

ACKs for top commit:
  MarcoFalke:
    cr ACK 2f0b25a

Tree-SHA512: 874ccd5bd19ecbbe91912171ac85af7a4658dc92f6db484ff3d03f07f1b9ba97e1c69d33a5c3ae5c5ec46cac3595a211f55fec0fbf81bac30d66a891c376ce26

src/rpc/blockchain.cpp

@@ -2136,7 +2136,6 @@ class CoinsViewScanReserver
 static RPCHelpMan scantxoutset()
 {
     return RPCHelpMan{"scantxoutset",
-        "\nEXPERIMENTAL warning: this call may be removed or changed in future releases.\n"
         "\nScans the unspent transaction output set for entries that match certain output descriptors.\n"
         "Examples of output descriptors are:\n"
         "    addr(<address>)                      Outputs whose scriptPubKey corresponds to the specified address (does not include P2PK)\n"