Use released Drain::flush instead of pinned git branch

This will be subsumed by a proper upgrade to v2.8.
For the time being, this makes it easier to test things out.

Author: Techcable

Cargo.toml

@@ -21,7 +21,7 @@ default = []
 path = "lib.rs"
 
 [dependencies]
-slog = { git = "https://github.com/Techcable/slog.git", branch = "feature/simple-flush-method" }
+slog = "2.8"
 thread_local = "1"
 take_mut = "0.2.0"
 crossbeam-channel = "0.5"