doc/filters: Fix option ranges for the sab filter.

Fixes ticket #5751.

doc/filters.texi

@@ -11219,16 +11219,16 @@ Set luma maximum difference between pixels to still be considered, must
 be a value in the 0.1-100.0 range, default value is 1.0.
 
 @item chroma_radius, cr
-Set chroma blur filter strength, must be a value in range 0.1-4.0. A
+Set chroma blur filter strength, must be a value in range -0.9-4.0. A
 greater value will result in a more blurred image, and in slower
 processing.
 
 @item chroma_pre_filter_radius, cpfr
-Set chroma pre-filter radius, must be a value in the 0.1-2.0 range.
+Set chroma pre-filter radius, must be a value in the -0.9-2.0 range.
 
 @item chroma_strength, cs
 Set chroma maximum difference between pixels to still be considered,
-must be a value in the 0.1-100.0 range.
+must be a value in the -0.9-100.0 range.
 @end table
 
 Each chroma option value, if not explicitly specified, is set to the