changelog: update to reflect `detached` api name

CHANGELOG.md

@@ -138,7 +138,7 @@ v0.25
   `git_merge_driver_source_file_options()` added as accessors to
   `git_merge_driver_source`.
 
-* `git_remote_create_unattached()` creates a remote that is not associated
+* `git_remote_create_detached()` creates a remote that is not associated
   to any repository (and does not apply configuration like 'insteadof' rules).
   This is mostly useful for e.g. emulating `git ls-remote` behavior.