Fix broken documentation introduced by fix for #334

doc/chapter-firststeps.txt

@@ -84,7 +84,7 @@ also contain comments, which start with the '#' character and go as far as the
 end of line. If you need to enter a configuration argument that contains
 spaces, use quotes (") around the whole argument. It's even possible to
 integrate the output of external commands into the configuration. The text
-between two backticks ("`") is evaluated as shell command, and its output is
+between two backticks ("\`") is evaluated as shell command, and its output is
 put on its place instead. This works like backtick evaluation in
 Bourne-compatible shells and allows users to use external information from the
 system within the configuration. Backticks can be escaped with a backslash