Fix typo in description of link to mozilla bug report writing guidelines.
Though the URL is misleading, we're indeed trying to write bug _reports_, not to add bugs.
Automerge-Triggered-By: @ned-deily
Article which goes into some detail about how to create a useful bug report.
This describes what kind of information is useful and why it is useful.
- `Bug Writing Guidelines <https://developer.mozilla.org/en-US/docs/Mozilla/QA/Bug_writing_guidelines>`_
+ `Bug Report Writing Guidelines <https://developer.mozilla.org/en-US/docs/Mozilla/QA/Bug_writing_guidelines>`_
Information about writing a good bug report. Some of this is specific to the
Mozilla project, but describes general good practices.