templatefilters: deprecate hgdate as {date|hgdate} is the default format

mercurial/templatefilters.py

@@ -241,7 +241,7 def hexfilter(text):
 @templatefilter('hgdate', intype=templateutil.date)
 def hgdate(text):
     """Date. Returns the date as a pair of numbers: "1157407993
-    25200" (Unix timestamp, timezone offset).
+    25200" (Unix timestamp, timezone offset). (DEPRECATED)
     """
     return "%d %d" % text