Update MessagePack

[jjonescz]

Resolves https://dev.azure.com/dnceng/internal/_componentGovernance/dotnet-sdk/alert/10371482?typeId=35105737&pipelinesTrackingFilter=0.

[marcpopMSFT]

/backport to release/10.0.1xx

[github-actions]

Started backporting to release/10.0.1xx: https://github.com/dotnet/sdk/actions/runs/17864198843

[github-actions]

@marcpopMSFT backporting to "release/10.0.1xx" failed, the patch most likely resulted in conflicts:

$ git am --3way --empty=keep --ignore-whitespace --keep-non-patch changes.patch

Applying: Update MessagePack
Using index info to reconstruct a base tree...
M	Directory.Packages.props
Falling back to patching base and 3-way merge...
Auto-merging Directory.Packages.props
CONFLICT (content): Merge conflict in Directory.Packages.props
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
hint: When you have resolved this problem, run "git am --continue".
hint: If you prefer to skip this patch, run "git am --skip" instead.
hint: To restore the original branch and stop patching, run "git am --abort".
hint: Disable this message with "git config set advice.mergeConflict false"
Patch failed at 0001 Update MessagePack
Error: The process '/usr/bin/git' failed with exit code 128

Please backport manually!