fix(deps): update rust crate async-openai to 0.28.0

Author: renovate[bot]

tiktoken-rs/Cargo.toml

@@ -18,7 +18,7 @@ debug = 1
 
 [dependencies]
 anyhow = "1.0.76"
-async-openai = { version = "0.14.2", optional = true }
+async-openai = { version = "0.28.0", optional = true }
 base64 = "0.22.0"
 bstr = "1.6.2"
 dhat = { version = "0.3.2", optional = true }