Fix delay dependency to git revision 849918a8dfb2

So we can test it with `blink` before a "crate" of `delay` is published.

Author: stappersg

Cargo.toml

@@ -29,7 +29,7 @@ all-mcus = []
 
 [dependencies]
 avr-config = { version = "2.0", features = ["cpu-frequency"] }
-avr_delay = { git = "https://github.com/avr-rust/delay", version = "0.4.0" }
+avr_delay = { git = "https://github.com/avr-rust/delay", rev = "849918a8dfb2" }
 avr-std-stub = { version = "1.0", optional = true }
 const_env--value = "0.1"
 target-cpu-macro = "0.1"