.NET: ci: Unblock Merge queue by disabling DurableTask TTL tests

[lokitoth]

The DurableTask Integration tests have some flakiness around the TTL tests. To unblock the queue we will disable them and create an issue #3463 to track fixing/re-enabling.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the Contribution Guidelines
• All unit tests pass, and I have added new tests where possible
• Is this a breaking change? If yes, add "[BREAKING]" prefix to the title of the PR.

[Copilot]

Pull request overview

This PR temporarily disables flaky Time-To-Live (TTL) integration tests in the DurableTask test suite to unblock the merge queue. The tests are experiencing intermittent failures with TaskCanceledException, and this change allows the team to address the flakiness without blocking ongoing development work. Issue #3463 has been created to track re-enabling these tests.

Changes:

• Changed the test category trait from "Integration" to "IntegrationDisabled" for the TimeToLiveTests class
• Updated the CI workflow to filter out tests with "IntegrationDisabled" category when running integration tests
• Minor whitespace cleanup in the workflow file

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
dotnet/tests/Microsoft.Agents.AI.DurableTask.IntegrationTests/TimeToLiveTests.cs	Changed test category from "Integration" to "IntegrationDisabled" to exclude TTL tests from CI runs
.github/workflows/dotnet-build-and-test.yml	Added test filter to exclude "IntegrationDisabled" tests and removed trailing whitespace