Remove defmt features from Cargo.toml

They are obsolete with defmt 0.3.
(See https://defmt.ferrous-systems.com/migration-02-03.html)

Author: jannic

Cargo.toml

@@ -41,22 +41,6 @@ pc-keyboard = "0.6"
 # Useful queues and other structures
 heapless = "0.7"
 
-[features]
-default = [
-    "defmt-default",
-]
-defmt-default = []
-# Enables trace logs
-defmt-trace = []
-# Enables debug logs
-defmt-debug = []
-# Enables info logs
-defmt-info = []
-# Enables warn logs
-defmt-warn = []
-# Enables error logs
-defmt-error = []
-
 [[bin]]
 name = "neotron-pico-bios"
 test = false