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:

• Fix #10581 – std.logger has an ostensibly broken example and wrong docs phobos#10582 (comment)
  • Fix #10581 – std.logger has an ostensibly broken example and wrong docs phobos#10582 (comment)
    • Fix #10581 – std.logger has an ostensibly broken example and wrong docs phobos#10582 (comment)

[CyberShadow]

I think #305 is trying to fix that.