build: bump rustc-demangle from 0.1.19 to 0.1.20

Bumps [rustc-demangle](https://github.com/alexcrichton/rustc-demangle) from 0.1.19 to 0.1.20.
- [Release notes](https://github.com/alexcrichton/rustc-demangle/releases)
- [Commits](https://github.com/alexcrichton/rustc-demangle/compare/0.1.19...0.1.20)

---
updated-dependencies:
- dependency-name: rustc-demangle
  dependency-type: indirect
  update-type: version-update:semver-patch
...

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

Cargo.lock

@@ -850,9 +850,9 @@ dependencies = [
 
 [[package]]
 name = "rustc-demangle"
-version = "0.1.19"
+version = "0.1.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "410f7acf3cb3a44527c5d9546bad4bf4e6c460915d5f9f2fc524498bfe8f70ce"
+checksum = "dead70b0b5e03e9c814bcb6b01e03e68f7c57a80aa48c72ec92152ab3e818d49"
 
 [[package]]
 name = "ryu"