Fix typo in expansion documentation (#14736)

Author: xcpky

book/src/command-line.md

@@ -15,7 +15,7 @@ By default, command arguments are split on tabs and space characters. `:open REA
 
 Double quotes may be used the same way, but double quotes _expand_ their inner content. `:echo "%{cursor_line}"` for example may print `1` because of the expansion for the `cursor_line` variable. `:echo '%{cursor_line}'` though prints `%{cursor_line}` literally: content within single quotes or backticks is interpreted as-is.
 
-On Unix systems the backslash character may be used to escape certain characters depending on where it is used. Within an argument which isn't surround in quotes, the backslash can be used to escape the space or tab characters: `:open a\ b.txt` is equivalent to `:open 'a b.txt'`. The backslash may also be used to escape quote characters (`'`, `` ` ``, `"`) or the percent token (`%`) when used at the beginning of an argument. `:echo \%%sh{foo}` for example prints `%sh{foo}` instead of invoking a `foo` shell command and `:echo \"quote` prints `"quote`. The backslash character is treated literally in any other situation on Unix systems and always on Windows: `:echo \n` always prints `\n`.
+On Unix systems the backslash character may be used to escape certain characters depending on where it is used. Within an argument which isn't surround in quotes, the backslash can be used to escape the space or tab characters: `:open a\ b.txt` is equivalent to `:open 'a b.txt'`. The backslash may also be used to escape quote characters (`'`, `` ` ``, `"`) or the percent token (`%`) when used at the beginning of an argument. `:echo \%sh{foo}` for example prints `%sh{foo}` instead of invoking a `foo` shell command and `:echo \"quote` prints `"quote`. The backslash character is treated literally in any other situation on Unix systems and always on Windows: `:echo \n` always prints `\n`.
 
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