Do no longer warn about missing Bugzilla references

[0xEAB]

Issue tracking of DMD, Phobos and friends has been moved from the DLF’s Bugzilla instance to GitHub. This bot still mentions Bugzilla and asks people to create Bugzilla issues in order to reference them.

Example:

• https://github.com/dlang/phobos/pull/10582#issuecomment-2533230607
  • https://github.com/dlang/phobos/pull/10582#issuecomment-2533232403
    • https://github.com/dlang/phobos/pull/10582#issuecomment-2533234405

[CyberShadow]

I think #305 is trying to fix that.