Update Rust crate diesel to 2.1.6 (#64)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Cargo.toml

@@ -16,14 +16,14 @@ default = [ "cockroach" ]
 [dependencies]
 bb8 = "0.8"
 async-trait = "0.1.80"
-diesel = { version = "2.1.0", default-features = false, features = [ "r2d2" ] }
+diesel = { version = "2.1.6", default-features = false, features = [ "r2d2" ] }
 futures = "0.3"
 thiserror = "1.0"
 tokio = { version = "1.32", default-features = false, features = [ "rt-multi-thread" ] }
 
 [dev-dependencies]
 anyhow = "1.0"
-diesel = { version = "2.1.0", features = [ "postgres", "r2d2" ] }
+diesel = { version = "2.1.6", features = [ "postgres", "r2d2" ] }
 libc = "0.2.150"
 tempfile = "3.8"
 tokio = { version = "1.32", features = [ "macros", "fs", "process" ] }