⬆️ Update rkyv requirement from 0.7 to 0.8 (HIT-SCIR#715)

Updates the requirements on [rkyv](https://github.com/rkyv/rkyv) to permit the latest version.
- [Release notes](https://github.com/rkyv/rkyv/releases)
- [Commits](rkyv/rkyv@v0.7.0...0.8.8)

---
updated-dependencies:
- dependency-name: rkyv
  dependency-type: direct:production
...

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

rust/ltp/Cargo.toml

@@ -55,7 +55,7 @@ apache-avro = { version = "0.17.0", optional = true }
 
 # Todo: Nocopy Serialize 更快地加载速度
 compact_str = { version = "0.8", optional = true }
-rkyv = { version = "0.7", optional = true }
+rkyv = { version = "0.8", optional = true }
 
 [features]
 default = []