fix(doc/README.md): Remove Copy engine references (#1978)

Author: SanderHestvik

doc/README.md

@@ -14,7 +14,7 @@ vi ~/.mackup.cfg
 You can specify the storage type Mackup will use to store your configuration
 files.
 
-For now, you have 4 options: `dropbox`, `google_drive`, `icloud`, `copy` and `file_system`.
+For now, you have 4 options: `dropbox`, `google_drive`, `icloud` and `file_system`.
 
 If none is specified, Mackup will try to use the default: `dropbox`.
 With the `dropbox` storage engine, Mackup will automatically figure out your
@@ -47,16 +47,6 @@ configuration files in the `~/Library/Mobile\ Documents/com\~apple\~CloudDocs/`
 engine = icloud
 ```
 
-### Copy
-
-If you choose the `copy` storage engine, Mackup will figure out
-where your Copy folder is and store your configuration files in it.
-
-```ini
-[storage]
-engine = copy
-```
-
 ### File System
 
 If you want to specify another directory, you can use the `file_system` engine