[FIX] website: fix the new design of the Banner snippet

In commit [1], the Banner snippet has been redesigned in order to be
in grid mode by default, to highlight some cool features of the editor.
However, some grid classes and attributes are missing or not well set:
- the first column has a `g-height-4` class despite having 8 rows: this
causes the vertical resize to not work correctly.
- the row does not have the `data-row-count` attribute, which is needed
to display the background grid correctly.

This commit fixes this by replacing the class by `g-height-8` and adding
the `data-row-count` attribute, which is set to 11 rows.

[1]: odoo@3cbdf75

task-3369695

closes odoo#136683

Signed-off-by: Quentin Smetz (qsm) <[email protected]>

Author: sobo-odoo

addons/website/views/snippets/s_banner.xml

@@ -4,8 +4,8 @@
 <template id="s_banner" name="Banner">
     <section class="s_banner pt96 pb96">
         <div class="container">
-            <div class="row s_nb_column_fixed o_grid_mode">
-                <div class="justify-content-center o_grid_item g-height-4 g-col-lg-5 col-lg-5" data-name="Box" style="z-index: 1; grid-area: 2 / 1 / 10 / 6;">
+            <div class="row s_nb_column_fixed o_grid_mode" data-row-count="11">
+                <div class="justify-content-center o_grid_item g-height-8 g-col-lg-5 col-lg-5" data-name="Box" style="z-index: 1; grid-area: 2 / 1 / 10 / 6;">
                     <h1><font style="font-size: 62px;">Sell Online. <strong>Easily.</strong></font></h1>
                     <p class="lead">This is a simple hero unit, a simple jumbotron-style component for calling extra attention to featured content or information.</p>
                     <div class="s_hr text-start pb32 pt4" data-snippet="s_hr" data-name="Separator">