Require sem-conv >= 1.38 to prevent fatal errors from missing classes

[ste93cry]

This PR updates the composer.json constraint for opentelemetry-php/sem-conv to require version 1.38. The HostIncubatingAttributes and OsIncubatingAttributes classes used by the Host resource detector were introduced in #1659 and first used in #1855. If a project upgrades the SDK while sem-conv remains outdated, it can lead to fatal errors when the detector tries to load classes that aren't available. This is exactly what happened in my case: Renovate updated the SDK because it was required in the project’s root composer.json, but sem-conv was only a transitive dependency and was therefore ignored, leaving an incompatible version installed.

Fatal error: Uncaught Error: Class "OpenTelemetry\SemConv\Incubating\Attributes\HostIncubatingAttributes" not found
in /var/www/app/vendor/open-telemetry/sdk/Resource/Detectors/Host.php:38

While version 1.36 technically contains the required classes, the SDK calls ResourceInfo::create with version 1.38, so I updated the requirement to that version to stay consistent with what the SDK expects.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 68.27%. Comparing base (e5a33a4) to head (6676c86).
⚠️ Report is 19 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #1903      +/-   ##
============================================
- Coverage     68.35%   68.27%   -0.08%     
  Complexity     3009     3009              
============================================
  Files           449      449              
  Lines          8798     8798              
============================================
- Hits           6014     6007       -7     
- Misses         2784     2791       +7     

Flag	Coverage Δ
8.2	68.20% <ø> (-0.13%)	⬇️
8.3	68.25% <ø> (+0.02%)	⬆️
8.4	?
8.5	67.38% <ø> (-0.04%)	⬇️

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