Merge bitcoin/bitcoin#24282: docs: Move explanation of hardened key syntax closer to KEY section

bac30e8 docs: Move explanation of hardened key syntax closer to KEY section (Bitcoin Hodler)

Pull request description:

  The line about "(Anywhere a `'` suffix is permitted to denote hardened derivation, the suffix `h` can be used instead.)" belongs with the section on KEY expressions, not following the unrelated TREE section.

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Tree-SHA512: 56fe97b89c02e67e94cab33b01e56f17f9b501b97036c5b35939dc4000a9d5e9afe4333869ba97bbe81372c538b7b2021a7d2520aba731400d8d0e62714d52b4

Author: fanquake

doc/descriptors.md

@@ -90,12 +90,12 @@ Descriptors consist of several types of expressions. The top level expression is
     - Optionally followed by a single `/*` or `/*'` final step to denote all (direct) unhardened or hardened children.
     - The usage of hardened derivation steps requires providing the private key.
 
+(Anywhere a `'` suffix is permitted to denote hardened derivation, the suffix `h` can be used instead.)
+
 `TREE` expressions:
 - any `SCRIPT` expression
 - An open brace `{`, a `TREE` expression, a comma `,`, a `TREE` expression, and a closing brace `}`
 
-(Anywhere a `'` suffix is permitted to denote hardened derivation, the suffix `h` can be used instead.)
-
 `ADDR` expressions are any type of supported address:
 - P2PKH addresses (base58, of the form `1...` for mainnet or `[nm]...` for testnet). Note that P2PKH addresses in descriptors cannot be used for P2PK outputs (use the `pk` function instead).
 - P2SH addresses (base58, of the form `3...` for mainnet or `2...` for testnet, defined in [BIP 13](https://github.com/bitcoin/bips/blob/master/bip-0013.mediawiki)).