doc-rst: pixfmt-nv16m: remove an empty column

The conversion added an empty column (probably, it was used on
DocBook just to increase spacing.

Remove it.

Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
diff --git a/Documentation/linux_tv/media/v4l/pixfmt-m420.rst b/Documentation/linux_tv/media/v4l/pixfmt-m420.rst
index f0304265..2f1f447 100644
--- a/Documentation/linux_tv/media/v4l/pixfmt-m420.rst
+++ b/Documentation/linux_tv/media/v4l/pixfmt-m420.rst
@@ -129,7 +129,6 @@
        -  
        -  1
 
-       -  
        -  2
 
        -  
@@ -144,7 +143,6 @@
        -  
        -  Y
 
-       -  
        -  Y
 
        -  
@@ -158,7 +156,6 @@
 
        -  
        -  
-       -  
        -  C
 
        -  
@@ -172,7 +169,6 @@
        -  
        -  Y
 
-       -  
        -  Y
 
        -  
@@ -191,7 +187,6 @@
        -  
        -  Y
 
-       -  
        -  Y
 
        -  
@@ -205,7 +200,6 @@
 
        -  
        -  
-       -  
        -  C
 
        -  
@@ -219,7 +213,6 @@
        -  
        -  Y
 
-       -  
        -  Y
 
        -