doc-rst: gen-errors: Improve table layout

Add a :widths: at the flat-table, to make it to look nicer.
Signed-off-by: NMauro Carvalho Chehab <mchehab@s-opensource.com>

Documentation/linux_tv/media/gen-errors.rst

@@ -12,6 +12,7 @@ Generic Error Codes
 .. flat-table:: Generic error codes
     :header-rows:  0
     :stub-columns: 0
+    :widths: 1 16
 
 
     -  .. row 1