chore(deps): bump acadrust to f76e41a for the xref save fix

Picks up the acadrust change that writes xref blocks as external
references instead of serializing their resolved contents as owned
entities. An xref attached with XATTACH now survives a save + reopen as
a reference instead of being bound/exploded into loose objects.

Closes #268

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Cargo.lock

@@ -71,7 +71,7 @@ checksum = "366ffbaa4442f4684d91e2cd7c5ea7c4ed8add41959a31447066e279e432b618"
 [[package]]
 name = "acadrust"
 version = "0.4.0"
-source = "git+https://github.com/HakanSeven12/acadrust?branch=main#e8e422a83742df747d2702f64cd87536b46e81fa"
+source = "git+https://github.com/HakanSeven12/acadrust?branch=main#f76e41adb47b09c66b3032d3727468e4303bcaf0"
 dependencies = [
  "ahash 0.8.12",
  "anyhow",