Update hifitime requirement from 3.8.5 to 4.0.0

Updates the requirements on [hifitime](https://github.com/nyx-space/hifitime) to permit the latest version.
- [Release notes](https://github.com/nyx-space/hifitime/releases)
- [Commits](nyx-space/hifitime@3.8.5...4.0.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

Cargo.toml

@@ -44,7 +44,7 @@ crate-type=["rlib", "cdylib", "staticlib"]
 [dependencies]
 cfg-if = "1.0.0"
 derive_more = { version = "0.99.17", optional = true }
-hifitime = { version = "3.8.5", default-features = false, optional = true }
+hifitime = { version = "4.0.0", default-features = false, optional = true }
 
 [features]
 default = ["std", "stdtime"]