patch 9.0.1981: not being able to scroll up in diff mode

Problem:  Cannot scroll up in diff mode with many filler lines and zero
          'scrolloff'.
Solution: Invalidate w_cline_row before calling comp_botline().

closes: #13256

Signed-off-by: Christian Brabandt <cb@256bit.org>
Co-authored-by: zeertzjq <zeertzjq@outlook.com>

src/version.c

@@ -704,6 +704,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1981,
 /**/
     1980,
 /**/