gitattributes.txt: Be more to the point in the filter driver description.

The description was meant to emphasizes that the project should remain
usable even if the filter driver was not used. This makes it more explicit
and removes the "here is rope to hang yourself" paraphrase.

Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/gitattributes.txt

@@ -164,11 +164,10 @@ but makes the filter a no-op passthru.
 The content filtering is done to massage the content into a
 shape that is more convenient for the platform, filesystem, and
 the user to use.  The keyword here is "more convenient" and not
-"turning something unusable into usable".  In other words, it is
-"hanging yourself because we gave you a long rope" if your
-project uses filtering mechanism in such a way that it makes
-your project unusable unless the checkout is done with a
-specific filter in effect.
+"turning something unusable into usable".  In other words, the
+intent is that if someone unsets the filter driver definition,
+or does not have the appropriate filter program, the project
+should still be usable.
 
 
 Interaction between checkin/checkout attributes