Update UnbrandedGeneratorVersion to 1.0.0-alpha.20260219.3#56363

jorgerangel-msft merged 4 commits intotypespec/update-http-client-1.0.0-alpha.20260219.3Azure/azure-sdk-for-net:typespec/update-http-client-1.0.0-alpha.20260219.3from

copilot/sub-pr-56357Azure/azure-sdk-for-net:copilot/sub-pr-56357Copy head branch name to clipboard