Auto merge of #1861 - jtgeibel:update/backtrace, r=carols10cents

Bump `backtrace` and `rustc-demangle`

This commit bumps a few additional packages that could be related to
the segfaults seen in production.  See #1805 for more info.

`cargo update -p backtrace -p rustc-demangle`

```
Updating backtrace v0.3.3 -> v0.3.38
Updating backtrace-sys v0.1.16 -> v0.1.31
Removing dbghelp-sys v0.2.0
Updating rustc-demangle v0.1.5 -> v0.1.16
```

Author: bors