Merge bitcoin#26352: doc: add scanblocks to list of descriptor RPCs

ff138f9 doc: add `scanblocks` to list of descriptor RPCs (Sebastian Falbesoner)

Pull request description:

  This is a tiny documentation follow-up to bitcoin#23549.

ACKs for top commit:
  aureleoules:
    ACK ff138f9
  shaavan:
    ACK ff138f9

Tree-SHA512: cc45b78c13ec4aa5bac688648f8e83f04a9ae54376e67371b280428f0253e2585cf0575fa51e3835d4c13c940559bfcdd88d7504bf97a81b2a73bb34a0db7577

Author: MacroFake

doc/descriptors.md

@@ -21,6 +21,8 @@ Supporting RPCs are:
 - `importdescriptors` takes as input descriptors to import into a descriptor wallet
   (since v0.21).
 - `listdescriptors` outputs descriptors imported into a descriptor wallet (since v22).
+- `scanblocks` takes as input descriptors to scan for in blocks and returns the
+   relevant blockhashes (since v25).
 
 This document describes the language. For the specifics on usage, see the RPC
 documentation for the functions mentioned above.