Update regex-syntax requirement from 0.7.1 to 0.8.0 (#4914)

Updates the requirements on [regex-syntax](https://github.com/rust-lang/regex) to permit the latest version.
- [Release notes](https://github.com/rust-lang/regex/releases)
- [Changelog](https://github.com/rust-lang/regex/blob/master/CHANGELOG.md)
- [Commits](https://github.com/rust-lang/regex/commits)

---
updated-dependencies:
- dependency-name: regex-syntax
  dependency-type: direct:production
...

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

arrow-string/Cargo.toml

@@ -40,5 +40,5 @@ arrow-schema = { workspace = true }
 arrow-array = { workspace = true }
 arrow-select = { workspace = true }
 regex = { version = "1.7.0", default-features = false, features = ["std", "unicode", "perf"] }
-regex-syntax = { version = "0.7.1", default-features = false, features = ["unicode"] }
+regex-syntax = { version = "0.8.0", default-features = false, features = ["unicode"] }
 num = { version = "0.4", default-features = false, features = ["std"] }