Fix duplicate docstring attributes in Measurement and Exemplar classes

[chimchim89]

Description

Fixes the duplicate attribute documentation caused by both napoleon and autodoc Sphinx extensions processing the same Attributes: sections in dataclass docstrings. This was flagged by TODO comments in both files referencing sphinx-doc/sphinx#8664.

Changes:

• docs/conf.py: Add napoleon_use_ivar = True so napoleon emits :ivar: fields instead of .. attribute:: directives, preventing autodoc from rendering the same attributes a second time
• measurement.py: Fix missing colon in Attributes: section and remove TODO comment
• exemplar.py: Fix missing colon in Attributes: section and remove TODO comment

Fixes # (no issue — fixing existing TODO comments in the codebase)

Type of change

• This change requires a documentation update

How Has This Been Tested?

Ran tox -e docs and tox -e ruff locally.

• tox -e ruff passes cleanly after auto-fix of trailing whitespace
• tox -e docs fails on both main and this branch with the same pre-existing unrelated error in opentelemetry._logs._internal.LogRecord (ambiguous cross-reference for Context). This is not caused by this PR.

Does This PR Require a Contrib Repo Change?

• No.

Checklist:

• Followed the style guidelines of this project
• Changelogs have been updated
• Unit tests have been added
• Documentation has been updated

[linux-foundation-easycla]

The committers listed above are authorized under a signed CLA.

• ✅ login: chimchim89 / name: Achal (a9b255a)

[tammy-baylis-swi]

Thanks for this. Maintainers will also review