[FIX] website: set s_text_cover background as primary

This commit sets `s_text_cover` default color preset to `o_cc4` to make
it look more like the header of "Anelusia theme" that was the initial
reference for the design of this snippet.

It also fixes a typo in `o_ccx` class introduced in commit [1] at the
same time actually.

[1]: https://github.com/odoo/odoo/commit/5ac340b1b27c9527463e2eed65fe2e7768b36702

task-3568868

closes odoo/odoo#140721

X-original-commit: 66f63ab23159fae86ba81369287e1cf8aac66d87
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/website/views/snippets/s_text_cover.xml

@@ -5,7 +5,7 @@
     <section class="s_text_cover">
         <div class="container-fluid">
             <div class="row">
-                <div class="o_colored_level o_cc o_cc_1 col-lg-5 pt160 pb160 px-5">
+                <div class="o_colored_level o_cc o_cc4 col-lg-5 pt160 pb160 px-5">
                     <h1 class="display-3">Sell Online. <br/>Easily.</h1>
                     <p class="lead">Write one or two paragraphs describing your product, services or a specific feature. To be successful your content needs to be useful to your readers.</p>
                     <a t-att-href="cta_btn_href" class="btn btn-primary"><t t-esc="cta_btn_text">Contact us</t></a>