Update crossbeam-epoch requirement from 0.7.0 to 0.8.0

Updates the requirements on [crossbeam-epoch](https://github.com/crossbeam-rs/crossbeam) to permit the latest version.
- [Release notes](https://github.com/crossbeam-rs/crossbeam/releases)
- [Changelog](https://github.com/crossbeam-rs/crossbeam/blob/master/CHANGELOG.md)
- [Commits](crossbeam-rs/crossbeam@crossbeam-epoch-0.7.0...crossbeam-epoch-0.8.0)

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

Cargo.toml

@@ -17,7 +17,7 @@ version = "2.0.1"
 repository = "bossmc/pinboard"
 
 [dependencies]
-crossbeam-epoch = "0.7.0"
+crossbeam-epoch = "0.8.0"
 
 [dev-dependencies]
 crossbeam = "0.7.1"