fix: MessagesSerializer error label for ID serialization

[VolodymyrBg]

The error context in MessagesSerializer::serialize() used "MessagesHandler" when mapping the error for message type ID serialization. This was inconsistent with the rest of the method, where "MessagesSerializer" is correctly used, and with
the convention in MessagesHandler::handle().

Using the correct component label improves log consistency, diagnostics, and filtering. No functional behavior changes; this is a logging/diagnostic fix.

[bilboquet]

thanks

[codecov]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 71.51%. Comparing base (c37d88d) to head (bf49e8a).
⚠️ Report is 18 commits behind head on main.

Files with missing lines	Patch %	Lines
massa-protocol-worker/src/messages.rs	0.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #4948      +/-   ##
==========================================
- Coverage   71.78%   71.51%   -0.27%     
==========================================
  Files         291      288       -3     
  Lines       51642    50351    -1291     
==========================================
- Hits        37069    36010    -1059     
+ Misses      14573    14341     -232     

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