Bump crossbeam from 0.8.3 to 0.8.4

Bumps [crossbeam](https://github.com/crossbeam-rs/crossbeam) from 0.8.3 to 0.8.4.
- [Release notes](https://github.com/crossbeam-rs/crossbeam/releases)
- [Changelog](https://github.com/crossbeam-rs/crossbeam/blob/master/CHANGELOG.md)
- [Commits](https://github.com/crossbeam-rs/crossbeam/compare/crossbeam-0.8.3...crossbeam-0.8.4)

---
updated-dependencies:
- dependency-name: crossbeam
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Cargo.lock

@@ -488,11 +488,10 @@ dependencies = [
 
 [[package]]
 name = "crossbeam"
-version = "0.8.3"
+version = "0.8.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6eb9105919ca8e40d437fc9cbb8f1975d916f1bd28afe795a48aae32a2cc8920"
+checksum = "1137cd7e7fc0fb5d3c5a8678be38ec56e819125d8d7907411fe24ccb943faca8"
 dependencies = [
- "cfg-if",
  "crossbeam-channel",
  "crossbeam-deque",
  "crossbeam-epoch",