Fix/clarify description of the noformat filter.

Originally committed as revision 20441 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavfilter/vf_format.c

@@ -134,7 +134,7 @@ AVFilter avfilter_vf_format = {
 
 AVFilter avfilter_vf_noformat = {
     .name      = "noformat",
-    .description = "Force libavfilter not to use any of the specified pixel formats as the input to the next filter.",
+    .description = "Force libavfilter not to use any of the specified pixel formats for the input to the next filter.",
 
     .init      = init,