Fix copy-paste class javadoc on OTLP AnyValue stateless marshalers

[thswlsqls]

Description

Three stateless marshalers in io.opentelemetry.exporter.internal.otlp carry a class javadoc copy-pasted from the KeyValue marshaler, so the description or the sibling {@link} no longer matches what the class marshals.

• AnyValueStatelessMarshaler marshals a single Value (AnyValue), not "key value pairs" — corrected to A Marshaler of {@link Value}.
• ArrayAnyValueStatelessMarshaler marshals a list of values (ArrayValue.VALUES) — corrected to A Marshaler of array values.
• KeyValueStatelessMarshaler's description is right, but its See {@link ...} pointed at AnyValueMarshaler. Every sibling stateless marshaler links to its own non-stateless counterpart (e.g. AttributeKeyValueStatelessMarshaler → KeyValueMarshaler), so this now links to KeyValueMarshaler.

Internal package only: no behavior, wire output, public API, or signature change.

Testing done

• Docs-only, test-exempt: no test added.
• ./gradlew :exporters:otlp:common:check passed (spotless, ErrorProne {@link} validation, jApiCmp, unit tests).
• No api diff, and no CHANGELOG.md entry (not user-facing).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.62%. Comparing base (4d974ba) to head (398d23b).
⚠️ Report is 42 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #8602      +/-   ##
============================================
+ Coverage     91.55%   91.62%   +0.07%     
- Complexity    10262    10321      +59     
============================================
  Files          1013     1013              
  Lines         27102    27287     +185     
  Branches       3182     3203      +21     
============================================
+ Hits          24812    25001     +189     
+ Misses         1565     1559       -6     
- Partials        725      727       +2     

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