Fix commit reference

Author: tritemio

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

@@ -300,7 +300,7 @@ Rather than remove a specific file with something like `rm file`, you have to re
 The reason to do it this way is speed – because Git doesn't have to check out each revision to disk before running your filter, the process can be much, much faster.
 You can accomplish the same task with `--tree-filter` if you want.
 The `--ignore-unmatch` option to `git rm` tells it not to error out if the pattern you're trying to remove isn't there.
-Finally, you ask `filter-branch` to rewrite your history only from the `6df7640` commit up, because you know that is where this problem started.
+Finally, you ask `filter-branch` to rewrite your history only from the `7b30847` commit up, because you know that is where this problem started.
 Otherwise, it will start from the beginning and will unnecessarily take longer.
 
 Your history no longer contains a reference to that file.