diff file was moved

Signed-off-by: Miek Gieben <miek@miek.nl>

Author: miekg

README.md

@@ -8,7 +8,7 @@ DNS version 2 is now available at <https://codeberg.org/miekg/dns>.
 The version here will only see specific fixes and nothing else. At some point this repo will be archived.
 
 **January 2026**: v2 should be a good replacement, and if not that is a bug to fix.
-See [this file describing the differences](https://codeberg.org/miekg/dns/src/branch/main/README-diff-with-v1.md).
+See [this file describing the differences](https://codeberg.org/miekg/dns/src/branch/main/_doc/README-v1-to-v2.md).
 
 # Alternative (more granular) approach to a DNS library