Fix header decoding on telemetry

[lferran]

Description

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How was this PR tested?

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[codecov]

Codecov Report

Attention: Patch coverage is 0% with 2 lines in your changes missing coverage. Please review.

Project coverage is 86.64%. Comparing base (c9a8419) to head (0ad4879).

Files	Patch %	Lines
...elemetry/src/nucliadb_telemetry/fastapi/tracing.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2367      +/-   ##
==========================================
+ Coverage   86.59%   86.64%   +0.04%     
==========================================
  Files         370      370              
  Lines       22665    22663       -2     
==========================================
+ Hits        19627    19636       +9     
+ Misses       3038     3027      -11     

Flag	Coverage Δ
nucliadb	73.57% <ø> (+0.08%)	⬆️
nucliadb-ingest	29.49% <ø> (ø)
nucliadb-reader	25.17% <ø> (ø)
nucliadb-search	37.35% <ø> (ø)
nucliadb-standalone	47.73% <ø> (ø)
nucliadb-train	46.69% <ø> (ø)
nucliadb-writer	40.47% <ø> (ø)
nucliadb_dataset	60.09% <ø> (ø)
nucliadb_models	85.40% <ø> (ø)
nucliadb_sdk	77.48% <ø> (ø)
nucliadb_sidecar	94.23% <ø> (ø)
nucliadb_telemetry	86.55% <0.00%> (-0.03%)	⬇️
nucliadb_utils	83.00% <ø> (ø)

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