Add celerybeat to gitignore.
Add celerybeat to gitignore.

johngian/mozillians,akatsoulas/mozillians,mozilla/mozillians,johngian/mozillians,akatsoulas/mozillians,mozilla/mozillians,akatsoulas/mozillians,johngian/mozillians,johngian/mozillians,mozilla/mozillians,akatsoulas/mozillians,mozilla/mozillians