Bump cpp_demangle from 0.3.5 to 0.4.0 in /src/agent

Bumps [cpp_demangle](https://github.com/gimli-rs/cpp_demangle) from 0.3.5 to 0.4.0.
- [Release notes](https://github.com/gimli-rs/cpp_demangle/releases)
- [Changelog](https://github.com/gimli-rs/cpp_demangle/blob/master/CHANGELOG.md)
- [Commits](https://github.com/gimli-rs/cpp_demangle/commits)

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

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

Author: dependabot[bot]

src/agent/Cargo.lock

@@ -12,7 +12,7 @@ symbol-filter = []  # Remove after impl'd
 [dependencies]
 anyhow = "1.0"
 bincode = "1.3"
-cpp_demangle = "0.3"
+cpp_demangle = "0.4"
 debugger = { path = "../debugger" }
 dunce = "1.0"
 fixedbitset = "0.4"

src/agent/coverage-legacy/Cargo.toml

@@ -54,7 +54,7 @@ debugger = { path = "../debugger" }
 winapi = { version = "0.3", features = ["impl-default", "psapi"] }
 
 [target.'cfg(target_family = "unix")'.dependencies]
-cpp_demangle = "0.3"
+cpp_demangle = "0.4"
 nix = "0.25"
 
 [target.'cfg(target_os = "linux")'.dependencies]