Fix Javadoc and comment in OSGi integration tests

[thswlsqls]

Description

• Add a class-level Javadoc to OpenTelemetryOsgiTest, matching the five sibling OSGi suite classes that all carry a /** Verifies ... in OSGi. */ summary. The wording reflects what the class exercises: the SDK (traces, metrics, logs) and the Context API.
• Fix the garbled comment in AutoconfigureDeclarativeConfigTest: the code uses System.setProperty, not addPropertiesSupplier, so the comment now explains that System.setProperty is required because property suppliers are not resolved until after the otel.config.file check.
• Comment/Javadoc only — no behavior, signature, or public API change.
• Related: module introduced in Finish adding OSGi support #8417.

Testing done

• Docs-only (Javadoc/comment), test-exempt: no test added.
• ./gradlew :integration-tests:osgi:spotlessApply then :spotlessCheck passed; compileTestSdkJava and compileTestAutoconfigureDeclarativeConfigJava compiled.
• OSGi Felix suites are heavyweight integration tests, not run for a comment/Javadoc-only change.
• Test module: no apidiff; no user-facing change, so no CHANGELOG entry.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.77%. Comparing base (824334c) to head (c97a705).

Additional details and impacted files

@@            Coverage Diff            @@
##               main    #8500   +/-   ##
=========================================
  Coverage     78.77%   78.77%           
  Complexity     8579     8579           
=========================================
  Files          1009     1009           
  Lines         28993    28993           
  Branches       3599     3599           
=========================================
  Hits          22839    22839           
  Misses         5311     5311           
  Partials        843      843           

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