Use fewer chrono features

The net of this is that the "time" and "wasi" transitive dependencies are
eliminated.

Author: jpgrayson

Cargo.lock

@@ -19,7 +19,7 @@ name = "stg"
 anyhow = "1.0"
 atty = "0.2"
 bstr = "0.2"
-chrono = "0.4"
+chrono = { version = "0.4", default-features = false, features = ["clock"] }
 clap = { version = "3.1", default-features = false, features = ["color", "std", "suggestions", "wrap_help"] }
 encoding_rs = "0.8"
 git2 = { version = "0.13", default-features = false }