Exclude collaborator in weekly new github issues report

[clarmso]

The current query includes COLLABORATOR users, which lists a few developers for the repository. Here are the users who opened new issues on the firefox-ios repository:

mysql> select github_user,github_author_association from report_github_bugs;
+----------------+---------------------------+
| github_user    | github_author_association |
+----------------+---------------------------+
| janbrasna      | CONTRIBUTOR               |
| leifwenzel     | NONE                      |
| nbhasin2       | COLLABORATOR              |
| dragosb01      | COLLABORATOR              |
| janbrasna      | CONTRIBUTOR               |
| thomoosterveer | NONE                      |
| Nmoleo64       | NONE                      |
| janbrasna      | CONTRIBUTOR               |
| overholt       | NONE                      |
| janbrasna      | CONTRIBUTOR               |
+----------------+---------------------------+

We should keep CONTRIBUTOR for now because this type of bug report features folks who aren't active developers in the repo. (I think janbrasna should be a COLLABORATOR just like the regular developer soon!)