[skip changelog] Correct configuration key name in documentation

Previously, this reference to Arduino CLI's `directories.downloads` configuration key misspelled the name as
"directories.download".

Author: per1234

docs/configuration.md

@@ -64,7 +64,7 @@ configuration file.
   - on Windows is: `{HOME}/AppData/Local/Arduino15`
   - on MacOS is: `{HOME}/Library/Arduino15`
 
-- The `directories.download` default is `{directories.data}/staging`. If the value of `{directories.data}` is changed in
+- The `directories.downloads` default is `{directories.data}/staging`. If the value of `{directories.data}` is changed in
   the configuration the user-specified value will be used.
 
 - The `directories.user` default is OS-dependent: