Merge #17752: doc: fix directory path for secp256k1 subtree in developer-notes

a5089f6 fix directory path for secp256k1 subtree in developer-notes (hackerrdave)

Pull request description:

  Documentation update to fix the directory path of the `secp256k1` subtree in the developer notes

ACKs for top commit:
  laanwj:
    ACK a5089f6

Tree-SHA512: d0986721d7091af26edaee769db78c9aabac25bbaddb2a1bfa96c7208187226e280e9c38897b5227ee6c9e40d5a1af86bb7c58e72c6a30a94a478c4bf54c086e

Author: fanquake

doc/developer-notes.md

@@ -820,7 +820,7 @@ Current subtrees include:
   - **Note**: Follow the instructions in [Upgrading LevelDB](#upgrading-leveldb) when
     merging upstream changes to the LevelDB subtree.
 
-- src/libsecp256k1
+- src/secp256k1
   - Upstream at https://github.com/bitcoin-core/secp256k1/ ; actively maintained by Core contributors.
 
 - src/crypto/ctaes