Fix SpanLimitsBuilder Javadoc to match non-negative argument check

[thswlsqls]

Fixes #8515

Description

• SpanLimitsBuilder's five count setters documented @param ... Must be positive. and @throws IllegalArgumentException if {@code ...} is not positive., but each checks value >= 0 ("must be non-negative") and accepts 0.
• Corrected the Javadoc to "Must not be negative." / "is negative." for setMaxNumberOfAttributes, setMaxNumberOfEvents, setMaxNumberOfLinks, setMaxNumberOfAttributesPerEvent, and setMaxNumberOfAttributesPerLink.
• This matches the sixth setter setMaxAttributeValueLength, which already documents the same >= 0 check correctly.
• The >= 0 behavior is intentional: PR Follow spec on span limits, batch processors #7030 relaxed these checks to follow the spec but left this Javadoc stale.

Testing done

• Docs-only, test-exempt: no behavior, signature, or public API change, so no test added.
• ./gradlew :sdk:trace:check passed (155 actionable tasks; test + spotlessCheck + ErrorProne/NullAway + jApiCmp). No docs/apidiffs change (Javadoc only). No CHANGELOG entry (not user-facing).

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 78.76%. Comparing base (824334c) to head (b6a8a48).

Additional details and impacted files

@@             Coverage Diff              @@
##               main    #8516      +/-   ##
============================================
- Coverage     78.77%   78.76%   -0.01%     
+ Complexity     8579     8578       -1     
============================================
  Files          1009     1009              
  Lines         28993    28993              
  Branches       3599     3599              
============================================
- Hits          22839    22837       -2     
- Misses         5311     5312       +1     
- Partials        843      844       +1     

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