Bump once_cell from 1.7.2 to 1.8.0 (#552)

Bumps [once_cell](https://github.com/matklad/once_cell) from 1.7.2 to 1.8.0.
- [Release notes](https://github.com/matklad/once_cell/releases)
- [Changelog](https://github.com/matklad/once_cell/blob/master/CHANGELOG.md)
- [Commits](matklad/once_cell@v1.7.2...v1.8.0)

---
updated-dependencies:
- dependency-name: once_cell
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]

Cargo.lock

@@ -73,7 +73,7 @@ log4rs = "1.0"
 cfg-if = "1"
 qrcode = { version = "0.12", default-features = false }
 pin-project = "1.0"
-once_cell = "1.7"
+once_cell = "1.8"
 thiserror = "1.0"
 
 spin = { version = "0.9", features = ["std"] }

crates/shadowsocks-service/Cargo.toml

@@ -40,7 +40,7 @@ cfg-if = "1"
 byte_string = "1.0"
 base64 = "0.13"
 url = "2.2"
-once_cell = "1.7"
+once_cell = "1.8"
 spin = { version = "0.9", features = ["std"] }
 pin-project = "1.0"
 bloomfilter = "1.0.2"