Update Test Failure Template (#38263)
Update Test Failure Template (#38263)

- Clarify instructions that this is specifically for dotnet/aspnetcore test failures
  - Avoids issues like https://github.com/dotnet/aspnetcore/issues/38248
  - Reasoning being, we want to avoid user issues being auto-tagged as `test-failure`s.
- Updates default title.
aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore,aspnet/AspNetCore