hgk: remove regsub, split on \r instead

No need to regsub all \r\n's to \n's,
we can just split on \r as well; this may
produce extra empty elements in the list,
but they won't match anyway.

contrib/hgk

@@ -472,9 +472,8 b' proc readrefs {} {'
             exit 2
         }
     }
-    regsub -all "\r\n" $heads "\n" heads
-
-    set lines [split $heads "\n"]
+
+    set lines [split $heads \r\n]
     foreach f $lines {
         set match ""
         regexp {changeset:\s+(\S+):(\S+)$} $f match id sha