build(deps): bump snafu from 0.6.8 to 0.6.9

Bumps [snafu](https://github.com/shepmaster/snafu) from 0.6.8 to 0.6.9.
- [Release notes](https://github.com/shepmaster/snafu/releases)
- [Changelog](https://github.com/shepmaster/snafu/blob/master/CHANGELOG.md)
- [Commits](https://github.com/shepmaster/snafu/compare/0.6.8...0.6.9)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Cargo.lock

@@ -1574,9 +1574,9 @@ checksum = "fbee7696b84bbf3d89a1c2eccff0850e3047ed46bfcd2e92c29a2d074d57e252"
 
 [[package]]
 name = "snafu"
-version = "0.6.8"
+version = "0.6.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c7f5aed652511f5c9123cf2afbe9c244c29db6effa2abb05c866e965c82405ce"
+checksum = "9c4e6046e4691afe918fd1b603fd6e515bcda5388a1092a9edbada307d159f09"
 dependencies = [
  "backtrace",
  "doc-comment",