Correct ambiguous 'ls' command

[N0NB]

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In the "Copying and Moving Files" section the '-F' option is passed to 'ls' to show two files and two directories. The next command moves one of the files to a directory and the following example shows a bare 'ls' but with one of the directories with a trailing '/' character (the result of the '-F' option).

This patch removes the ambiguity by showing the result when '-F' is passed to 'ls' by adding the option to the command and showing both directories with trailing '/' characters.

This ambiguity is also present in the original book available from: https://www.oreilly.com/openbook/utp/