fixes bug 992410 - Remove stale content for "crash_type" in reports tab on report list

@rhelmer r?
[There's no column called "crash_type"](https://github.com/peterbe/socorro/blob/31e777e7b6e667eacef97647254174b3bd427b79/webapp-django/crashstats/crashstats/views.py#L1277-L1292)