docs(datadog): Correct an erroneous reference to the opentelemetry_sdk crate

[arusahni]

Fixes #
Design discussion issue (if applicable) #

Changes

The name of the crate in the batched/performance example is incorrect -- it should be opentelemetry_sdk, not opentelemetry.

Merge requirement checklist

• CONTRIBUTING guidelines followed
• Unit tests added/updated (if applicable)
• Appropriate CHANGELOG.md files updated for non-trivial, user-facing changes
• Changes in public API reviewed (if applicable)

[linux-foundation-easycla]

• ✅login: arusahni / (856ff20)

The committers listed above are authorized under a signed CLA.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 54.1%. Comparing base (4d9b52f) to head (856ff20).
Report is 1 commits behind head on main.

Additional details and impacted files

@@          Coverage Diff          @@
##            main    #157   +/-   ##
=====================================
  Coverage   54.1%   54.1%           
=====================================
  Files         42      42           
  Lines       6282    6282           
=====================================
  Hits        3400    3400           
  Misses      2882    2882           

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