Update min OT version and remove Python 3.8 support

[jeremydvoss]

Description

Update to latest version of OTel. This breaking change led to this fix, but min version was not updated. Additionally, Along with newer versions of OTel, we are dropping support for Python 3.8.

All SDK Contribution checklist:

• The pull request does not introduce [breaking changes]
• CHANGELOG is updated for new features, bug fixes or other significant changes.
• I have read the contribution guidelines.

General Guidelines and Best Practices

• Title of the pull request is clear and informative.
• There are a small number of commits, each of which have an informative message. This means that previously merged commits do not appear in the history of the PR. For more information on cleaning up the commits in your PR, see this page.

Testing Guidelines

• Pull request includes test coverage for the included changes.

[Copilot]

Pull Request Overview

This PR updates the OpenTelemetry dependency versions from 1.26 to 1.35 and removes Python 3.8 support from the azure-monitor-opentelemetry-exporter package. The changes align with the deprecation of Python 3.8 and update to newer OpenTelemetry versions.

Key changes:

• Removed Python 3.8 classifier from setup.py
• Updated OpenTelemetry API and SDK dependencies from ~1.26 to ~1.35
• Added changelog entry documenting these changes

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
setup.py	Removed Python 3.8 classifier and updated OpenTelemetry dependencies to version 1.35
CHANGELOG.md	Added entry documenting the OpenTelemetry version update and Python 3.8 support removal

[rads-1996]

LGTM