UserGuide: Remove section "Changing Save Location"

The UserGuide claims that the save location of the addressbook data can
be changed via command line parameters.

That feature is not fully implemented. As such, addressbook data is
always saved in addressbook.txt and cannot be changed.

Let's remove the section "Changing Save Location". We can restore this
section after the feature is fully implemented.

doc/UserGuide.md

@@ -106,13 +106,4 @@ Format: `exit`
 
 ## Saving the data 
 Address book data are saved in the hard disk automatically after any command that changes the data.<br>
-There is no need to save manually.
-
-## Changing the save location
-Address book data are saved in a file called `addressbook.txt` in the project root folder.
-You can change the location by specifying the file path as a program argument.<br>
-
-> The file name must end in `.txt` for it to be acceptable to the program.
->
-> When running the program inside IntelliJ, you can
-  [set command line parameters before running the program](https://stackoverflow.com/a/2066465).
+There is no need to save manually. Address book data are saved in a file called `addressbook.txt` in the project root folder.