fix(azuredevops): handle 204 No Content in collectApiTimelineRecords timeline response

[bujjibabukatta]

Summary

Fixes the collectApiTimelineRecords subtask failing when the Azure DevOps
Timeline API returns 204 No Content for deleted or empty builds.

Root Cause

ignoreInvalidTimelineResponse() only guarded against 404 Not Found.
When a 204 No Content response was received, execution fell through to
io.ReadAll(res.Body) on an empty body. While the downstream empty-body
check would eventually skip the record, reading the body of a 204 response
before checking the status code is unsafe — some HTTP clients/proxies set
Body = nil on 204, which causes a nil-pointer panic.

Fix

Added an explicit http.StatusNoContent guard alongside the existing
http.StatusNotFound check, before the body is ever read.

Changes

• tasks/shared.go — extend the status guard in ignoreInvalidTimelineResponse
  to include 204 No Content
• tasks/shared_test.go — add TestIgnoreInvalidTimelineResponse_204 to
  cover the new guard

Testing

All existing tests continue to pass. New test TestIgnoreInvalidTimelineResponse_204
verifies that a 204 response returns api.ErrIgnoreAndContinue without
reading the body.

Related

Closes #8944

[bujjibabukatta]

Hi @klesh could you please review and approve pull request?