git-filter-repo.txt: fix nested bullets to render correctly

Signed-off-by: Elijah Newren <newren@gmail.com>

Documentation/git-filter-repo.txt

@@ -1049,9 +1049,9 @@ the user when it detects an issue:
   * When rewriting commit hashes in commit messages, there are a variety
     of cases when the hash will not be updated (whenever this happens, a
     note is written to `.git/filter-repo/suboptimal-issues`):
-    * if a commit hash does not correspond to a commit in the old repo
-    * if a commit hash corresponds to a commit that gets pruned
-    * if an abbreviated hash is not unique
+    ** if a commit hash does not correspond to a commit in the old repo
+    ** if a commit hash corresponds to a commit that gets pruned
+    ** if an abbreviated hash is not unique
 
   * Pruning of empty commits can cause a merge commit to lose an entire
     ancestry line and become a non-merge.  If the merge commit had no