Add ini classification to source block in refspec.asc

Author: crd

book/10-git-internals/sections/refspec.asc

@@ -77,7 +77,7 @@ If you want to always fetch the `master` and `experiment` branches, add two line
 
 You can't use partial globs in the pattern, so this would be invalid:
 
-[source]
+[source,ini]
 ----
 fetch = +refs/heads/qa*:refs/remotes/origin/qa*
 ----