Update msgpack fork dependency (#35988) (#36043)

(cherry picked from commit 17939826efa20a97f087b3d390ec5136df350bae)

Co-authored-by: Mattermost Build <build@mattermost.com>

server/go.sum

@@ -423,8 +423,8 @@ github.com/mattermost/mattermost/server/public v0.1.12 h1:qlIU/llY0FWdHWQPtvncdd
 github.com/mattermost/mattermost/server/public v0.1.12/go.mod h1:3RJZfl7sMedX6ihX+JMFOIAzCHhd0WQnuez+UFQS80k=
 github.com/mattermost/morph v1.1.0 h1:Q9vrJbeM3s2jfweGheq12EFIzdNp9a/6IovcbvOQ6Cw=
 github.com/mattermost/morph v1.1.0/go.mod h1:gD+EaqX2UMyyuzmF4PFh4r33XneQ8Nzi+0E8nXjMa3A=
-github.com/mattermost/msgpack/v5 v5.0.0-20260120151306-2f9c67d7e57f h1:tAXeRJSWo6EK7wDq1TcxMHIxHRyjrE62ihvsigdg4Q0=
-github.com/mattermost/msgpack/v5 v5.0.0-20260120151306-2f9c67d7e57f/go.mod h1:GaZTsDaehaPpQVyxrf5mtQlH+pc21PIudVV/E3rRQok=
+github.com/mattermost/msgpack/v5 v5.0.0-20260408165622-cadfad56a815 h1:uOi89NvrFmDngqMKjlLDxi+MNzJQLA3TqcU2p8czv34=
+github.com/mattermost/msgpack/v5 v5.0.0-20260408165622-cadfad56a815/go.mod h1:GaZTsDaehaPpQVyxrf5mtQlH+pc21PIudVV/E3rRQok=
 github.com/mattermost/rsc v0.0.0-20160330161541-bbaefb05eaa0 h1:G9tL6JXRBMzjuD1kkBtcnd42kUiT6QDwxfFYu7adM6o=
 github.com/mattermost/rsc v0.0.0-20160330161541-bbaefb05eaa0/go.mod h1:nV5bfVpT//+B1RPD2JvRnxbkLmJEYXmRaaVl15fsXjs=
 github.com/mattermost/squirrel v0.5.0 h1:81QPS0aA+inQbpA7Pzmv6O9sWwB6VaBh/VYw3oJf8ZY=