patchbomb: use a list instead of indented paragraphs

hgext/patchbomb.py

@@ -14,11 +14,9 b' Each patch email has a Subject line of "'
 first line of the changeset description as the subject text. The
 message contains two or three body parts:
 
-  The changeset description.
-
-  [Optional] The result of running diffstat on the patch.
-
-  The patch itself, as generated by "hg export".
+- The changeset description.
+- [Optional] The result of running diffstat on the patch.
+- The patch itself, as generated by "hg export".
 
 Each message refers to the first in the series using the In-Reply-To
 and References headers, so they will show up as a sequence in threaded