Fix a typo

Author: shengbinmeng

book/08-customizing-git/sections/config.asc

@@ -421,7 +421,7 @@ The three that are turned on by default are `blank-at-eol`, which looks for spac
 The three that are disabled by default but can be turned on are `indent-with-non-tab`, which looks for lines that begin with spaces instead of tabs (and is controlled by the `tabwidth` option); `tab-in-indent`, which watches for tabs in the indentation portion of a line; and `cr-at-eol`, which tells Git that carriage returns at the end of lines are OK.
 
 You can tell Git which of these you want enabled by setting `core.whitespace` to the values you want on or off, separated by commas.
-You can disable settings by prepending a - in front of the value, or use default value of settings by leaving them out of the setting string.
+You can disable settings by prepending a `-` in front of the value, or use default value of settings by leaving them out of the setting string.
 For example, if you want all but `space-before-tab` to be set, you can do this (with `trailing-space` being a short-hand to cover both `blank-at-eol` and `blank-at-eof`):
 
 [source,console]