Merge bitcoin#17596: doc: Change doxygen URL to doxygen.bitcoincore.org

41d7db0 doc: Change doxygen URL to doxygen.bitcoincore.org (Wladimir J. van der Laan)

Pull request description:

  The bitcoin core doxygen documentation has moved to https://doxygen.bitcoincore.org, see bitcoin-core/bitcoincore.org#681

  (the old URL still works as a redirect)

ACKs for top commit:
  Sjors:
    ACK 41d7db0 based on a short spot check.
  fanquake:
    ACK 41d7db0 - also checked the redirect.

Tree-SHA512: e6fa0477b7825e3557c1b3bed8c5a37c33188ddcba43e6a19f95d86618408f7d04bbaeb64bd79181930c5af1252ca5c462e3f7a850bfffa39a8f62bcccbb4260

Author: fanquake

doc/README.md

@@ -54,7 +54,7 @@ The Bitcoin repo's [root README](/README.md) contains relevant information on th
 - [Productivity Notes](productivity.md)
 - [Release Notes](release-notes.md)
 - [Release Process](release-process.md)
-- [Source Code Documentation (External Link)](https://dev.visucore.com/bitcoin/doxygen/)
+- [Source Code Documentation (External Link)](https://doxygen.bitcoincore.org/)
 - [Translation Process](translation_process.md)
 - [Translation Strings Policy](translation_strings_policy.md)
 - [JSON-RPC Interface](JSON-RPC-interface.md)