Help: Document that file(GLOB) result is sorted

It has been sorted since commit v3.6.0-rc1~54^2 (file: Sort GLOB results
to make it deterministic, 2016-05-14).  That commit left the order
unspecified in the documentation, but has been stable long enough to
document now.

Help/command/file.rst

@@ -105,9 +105,7 @@ Generate a list of files that match the ``<globbing-expressions>`` and
 store it into the ``<variable>``.  Globbing expressions are similar to
 regular expressions, but much simpler.  If ``RELATIVE`` flag is
 specified, the results will be returned as relative paths to the given
-path.  No specific order of results is defined other than that it is
-deterministic.  If order is important then sort the list explicitly
-(e.g. using the :command:`list(SORT)` command).
+path.  The results will be ordered lexicographically.
 
 By default ``GLOB`` lists directories - directories are omited in result if
 ``LIST_DIRECTORIES`` is set to false.