Fix typo preventing syntax highlighting for source block

Author: crd

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

@@ -304,7 +304,7 @@ Last commit date: Tue Apr 21 08:38:48 2009 -0700 by Scott Chacon
 
 The substitutions can include for example the commit message and any git notes, and git log can do simple word wrapping:
 
-[source.console]
+[source,console]
 ----
 $ echo '$Format:Last commit: %h by %aN at %cd%n%+w(76,6,9)%B$' > LAST_COMMIT
 $ git commit -am 'export-subst uses git log's custom formatter