ECC-2220 Fix inadvertent string truncation in uncompressed BUFR messages

[tomas-kral]

This removes now obsolete workaround for ECC-1623. The root issue had been fixed since eccodes 2.31.0. Turns out the workaround had a bug where setting string keys on uncompressed messages would truncate the strings.

Description

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

[codecov-commenter]

Codecov Report

❌ Patch coverage is 93.75000% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 30.19%. Comparing base (8e875e2) to head (1d91ce2).

Files with missing lines	Patch %	Lines
eccodes/highlevel/_bufr/coder.py	0.00%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #155      +/-   ##
===========================================
+ Coverage    30.01%   30.19%   +0.17%     
===========================================
  Files           34       34              
  Lines         6180     6193      +13     
  Branches       743      742       -1     
===========================================
+ Hits          1855     1870      +15     
+ Misses        4296     4294       -2     
  Partials        29       29              

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