README: fix copy-pasta in url

Author: keszybz

README.md

@@ -15,7 +15,7 @@ The new `--package-metadata` option provided by `bfd`, `gold`, `mold`, and `lld`
 It also provides scripts to extract and display `.note.dlopen` ELF notes
 that are used to describe libraries loaded via `dlopen(3)`.
 
-See [`dlopen()` Metadata for ELF Files](https://systemd.io/ELF_PACKAGE_METADATA/)
+See [`dlopen()` Metadata for ELF Files](https://systemd.io/ELF_DLOPEN_METADATA/)
 for the overview and details.
 
 ## Requirements