help: don't search randomly for help data - trust util.datapath

The search was introduced in c904e76e3834 without a convincing explanation why
it should be necessary ... except for consistency with templater handling.

Now, just keep it simple.

mercurial/help.py

@@ -129,11 +129,7 b' def loaddoc(topic):'
     """Return a delayed loader for help/topic.txt."""
 
     def loader():
-        for dir in ('.', '..'):
-            docdir = os.path.join(util.datapath, dir, 'help')
-            if os.path.isdir(docdir):
-                break
-
+        docdir = os.path.join(util.datapath, 'help')
         path = os.path.join(docdir, topic + ".txt")
         doc = gettext(util.readfile(path))
         for rewriter in helphooks.get(topic, []):