build(deps): update deadpool requirement from 0.9.5 to 0.12.0

Updates the requirements on [deadpool](https://github.com/bikeshedder/deadpool) to permit the latest version.
- [Changelog](https://github.com/bikeshedder/deadpool/blob/master/CHANGELOG.md)
- [Commits](deadpool-rs/deadpool@deadpool-v0.9.5...deadpool-v0.12.0)

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

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

Cargo.toml

@@ -15,7 +15,7 @@ dotenv = { version = "0.15.0", default-features = false }
 tokio = { version = "1.19.2", default-features = false, optional = true }
 tokio-postgres = { version = "0.7.6", default-features = false }
 deadpool-postgres = { version = "0.10.2", default-features = false }
-deadpool = { version = "0.9.5", default-features = false }
+deadpool = { version = "0.12.0", default-features = false }
 futures = "0.3"
 
 [features]