Merge bitcoin#28037: rpc: Drop migratewallet experimental warning

f1684bb rpc: mention that migratewallet can take a while (Andrew Chow)
9ecff99 rpc: Drop migratewallet experimental warning (Andrew Chow)

Pull request description:

  The migration process itself hasn't fundamentally changed since it was added, so I think it's reasonable to say that it is no longer experimental.

ACKs for top commit:
  maflcko:
    lgtm ACK f1684bb
  josibake:
    ACK bitcoin@f1684bb
  furszy:
    ACK bitcoin@f1684bb
  ryanofsky:
    Code review ACK f1684bb
  willcl-ark:
    ACK f1684bb

Tree-SHA512: 99b176cddbf3878c76bd4c80c030106200bf03139785e26dbae3341e1a675b623a13cd6dc7a0bb78344335bf859ae7548d97b2b58eb650c6e7b305d7cdc86e40

Author: fanquake

src/wallet/rpc/wallet.cpp

@@ -1061,13 +1061,13 @@ RPCHelpMan simulaterawtransaction()
 static RPCHelpMan migratewallet()
 {
     return RPCHelpMan{"migratewallet",
-        "EXPERIMENTAL warning: This call may not work as expected and may be changed in future releases\n"
         "\nMigrate the wallet to a descriptor wallet.\n"
         "A new wallet backup will need to be made.\n"
         "\nThe migration process will create a backup of the wallet before migrating. This backup\n"
         "file will be named <wallet name>-<timestamp>.legacy.bak and can be found in the directory\n"
         "for this wallet. In the event of an incorrect migration, the backup can be restored using restorewallet."
-        "\nEncrypted wallets must have the passphrase provided as an argument to this call.",
+        "\nEncrypted wallets must have the passphrase provided as an argument to this call.\n"
+        "\nThis RPC may take a long time to complete. Increasing the RPC client timeout is recommended.",
         {
             {"wallet_name", RPCArg::Type::STR, RPCArg::DefaultHint{"the wallet name from the RPC endpoint"}, "The name of the wallet to migrate. If provided both here and in the RPC endpoint, the two must be identical."},
             {"passphrase", RPCArg::Type::STR, RPCArg::Optional::OMITTED, "The wallet passphrase"},