[FIX] web_editor: report 2 columns must be side by side

To reproduce
============
- on studio > create new report from internal layout
- execute 2 columns command --> the second column will be under the first one

Problem
=======
the browser finds out that the `iframe` is small to keep two `col-lg-6` side by side.

Solution
========
use `col-6` instead, like in 17

opw-3585043

closes odoo/odoo#147074

X-original-commit: 246f42baf76b308210a2b03d46a6143ace4bb7cc
Signed-off-by: Antoine Guenet (age) <age@odoo.com>
Signed-off-by: Abdelouahab Laaroussi (abla) <abla@odoo.com>

addons/web_editor/static/src/js/editor/odoo-editor/src/base_style.scss

@@ -8,7 +8,7 @@ li.oe-nested {
         padding: 0.5rem;
     }
 }
-$sizes: 'xs', 'sm', 'md', 'lg', 'xl', 'xxl';
+$sizes: '', 'xs-', 'sm-', 'md-', 'lg-', 'xl-', 'xxl-';
 .o_text_columns {
     max-width: 100% !important;
     padding: 0 !important;
@@ -17,10 +17,10 @@ $sizes: 'xs', 'sm', 'md', 'lg', 'xl', 'xxl';
     margin: 0 !important;
     @each $size in $sizes {
         @for $i from 1 through 12 {
-            & > .col-#{$size}-#{$i}:first-of-type {
+            & > .col-#{$size}#{$i}:first-of-type {
                 padding-left: 0;
             }
-            & > .col-#{$size}-#{$i}:last-of-type {
+            & > .col-#{$size}#{$i}:last-of-type {
                 padding-right: 0;
             }
         }