Remove invalid comments

Removed comments that inherited from VP9 and were invalid currently.

Change-Id: I4fa33f508b5420ce8252beaae8cc930e6d933b55
diff --git a/aom/aomcx.h b/aom/aomcx.h
index 9703cf8..9546a54 100644
--- a/aom/aomcx.h
+++ b/aom/aomcx.h
@@ -300,9 +300,6 @@
    *             2 = 4 tile columns
    *             .....
    *             n = 2**n tile columns
-   * The requested tile columns will be capped by encoder based on image size
-   * limitation (The minimum width of a tile column is 256 pixel, the maximum
-   * is 4096).
    *
    * By default, the value is 0, i.e. one single column tile for entire image.
    */