help: fix keyword search result formatting

This patch fixes the broken formatting of keyword search results. Some blank
lines were missing from the RST markup, which caused markup to be printed.

mercurial/commands.py

@@ -3332,6 +3332,7 b' def help_(ui, name=None, unknowncmd=Fals'
             if matches[t]:
                 rst.append('%s:\n\n' % title)
                 rst.extend(minirst.maketable(matches[t], 1))
+                rst.append('\n')
     elif name and name != 'shortlist':
         i = None
         if unknowncmd: