Update phf requirement from 0.11 to 0.12

Updates the requirements on [phf](https://github.com/rust-phf/rust-phf) to permit the latest version.
- [Release notes](https://github.com/rust-phf/rust-phf/releases)
- [Changelog](https://github.com/rust-phf/rust-phf/blob/master/RELEASE_PROCESS.md)
- [Commits](rust-phf/rust-phf@phf-v0.11.1...v0.12.1)

---
updated-dependencies:
- dependency-name: phf
  dependency-version: 0.12.1
  dependency-type: direct:production
...

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

Author: dependabot[bot]

tokio-postgres/Cargo.toml

@@ -57,7 +57,7 @@ log = "0.4"
 parking_lot = "0.12"
 percent-encoding = "2.0"
 pin-project-lite = "0.2"
-phf = "0.11"
+phf = "0.12"
 postgres-protocol = { version = "0.6.8", path = "../postgres-protocol" }
 postgres-types = { version = "0.2.9", path = "../postgres-types" }
 tokio = { version = "1.27", features = ["io-util"] }