extract-m4a: quiet logging

scripts/extract-m4a.nu

···
     let file = $file | path expand
     let parsed_path = $file | path parse
 
-    log info $"Extracting `($file)`"
+    log debug $"Extracting `($file)`"
 
     if $parsed_path.extension != "m4a" {
         error make {
···
     #   -c:a copy -> Copy codec
     #   -vn       -> No video
 
-    log info $"Extracted `($file)` to `($output)`"
+    log debug $"Extracted `($file)` to `($output)`"
 }