Bump msgpack from v1.8.0 to v1.8.3

Resolves:

- https://www.cve.org/CVERecord/SearchResults?query=CVE-2026-54522

Author: leeky

Gemfile.lock

@@ -308,7 +308,7 @@ GEM
     minitest (6.0.6)
       drb (~> 2.0)
       prism (~> 1.5)
-    msgpack (1.8.0)
+    msgpack (1.8.3)
     multi_test (1.1.0)
     net-http (0.9.1)
       uri (>= 0.11.1)