Upgrade rustc for firefox-65.0
|Reported by:||Owned by:||Bruce Dubbs|
Firefox-65.0 is expected to be released on 20th January, after a "soft freeze" on 21st January. It will need at least version 1.30 of rust. As in past practice, we should prefer the latest version.
The 1.30 series was first released on 6th December (point release on about 20th December) which suggests that 1.32.0 will be released around the 23rd January because the minor versions seem to be on a 7-week cycle.
We can probably use 1.31.1, but never trust release schedules! (there might be late changes somewhere which require a later version).