doc: use getxpub in basic multisig descriptor example

doc/descriptors.md

@@ -165,8 +165,8 @@ The basic steps are:
 
   1. Every participant generates an xpub. The most straightforward way is to create a new descriptor wallet which we will refer to as
      the participant's signer wallet. Avoid reusing this wallet for any purpose other than signing transactions from the
-     corresponding multisig we are about to create. Hint: extract the wallet's xpubs using `listdescriptors` and pick the one from the
-     `pkh` descriptor since it's least likely to be accidentally reused (legacy addresses)
+     corresponding multisig we are about to create. Hint: extract the wallet's xpubs using `getxpub m/44h/0h/0h` (`m/44h/1h/0h` for testnet and signet). This reuses keys from the
+     `pkh` descriptor (legacy addresses), since these are the least likely to be accidentally reused. A future update to `importdescriptors` may add support for derivation the corresponding private keys of arbitrary derivations, such as BIP87's `m/87h`. That would prevent key reuse entirely.
   2. Create a watch-only descriptor wallet (blank, private keys disabled). Now the multisig is created by importing the two descriptors:
      `wsh(sortedmulti(<M>,XPUB1/0/*,XPUB2/0/*,…,XPUBN/0/*))` and `wsh(sortedmulti(<M>,XPUB1/1/*,XPUB2/1/*,…,XPUBN/1/*))`
      (one descriptor w/ `0` for receiving addresses and another w/ `1` for change). Every participant does this