Use env_logger w/o unnecessary regex feature to reduce binary size

This reduces size of the swayr binary by ~57 %. It doesn't affect the
size of the swayrd binary because swayrd uses regex.

When building with lto = true, opt-level = "z" and panic = "abort" on
Alpine Linux: swayr 1 294 kiB -> 554 kiB

Cargo.lock

@@ -99,7 +99,6 @@ dependencies = [
  "atty",
  "humantime",
  "log",
- "regex",
  "termcolor",
 ]
 

Cargo.toml

@@ -21,4 +21,4 @@ lazy_static = "1.4.0"
 rand = "0.8.4"
 rt-format = "0.3.0"
 log = "0.4"
-env_logger = "0.9.0"
+env_logger = { version = "0.9.0", default-features = false, features = ["termcolor", "atty", "humantime"] }  # without regex