Merge bitcoin/bitcoin#33630: doc: correct topology requirements in submitpackage helptext

3d22282 [doc] correct topology requirements in submitpackage helptext (glozow)

Pull request description:

  This doc is outdated since #31385. Also made it explicit that a singleton is ok.

  Can be backported to 30.x, but doesn't need to be backported earlier ("if any" covers #31096).

ACKs for top commit:
  janb84:
    ACK 3d22282
  instagibbs:
    ACK 3d22282

Tree-SHA512: 95e40630a5b2a571029c0657c20a5e2a1cf1789913b868cee314c1a9fcb9a09fccdd3c87f3f15a8eb95c5ff9b83f8adee0661f86619bf21965866b6f6a76dfd0

Author: fanquake

src/rpc/mempool.cpp

@@ -936,8 +936,9 @@ static RPCHelpMan submitpackage()
         ,
         {
             {"package", RPCArg::Type::ARR, RPCArg::Optional::NO, "An array of raw transactions.\n"
-                "The package must solely consist of a child transaction and all of its unconfirmed parents, if any. None of the parents may depend on each other.\n"
-                "The package must be topologically sorted, with the child being the last element in the array.",
+                "The package must consist of a transaction with (some, all, or none of) its unconfirmed parents. A single transaction is permitted.\n"
+                "None of the parents may depend on each other. Parents that are already in mempool do not need to be present in the package.\n"
+                "The package must be topologically sorted, with the child being the last element in the array if there are multiple elements.",
                 {
                     {"rawtx", RPCArg::Type::STR_HEX, RPCArg::Optional::OMITTED, ""},
                 },