[IMP] theme_*: remove some snippets hard coded background color

This is the direct following of the PR [1].

Some themes "hard code" the background colors of some snippets, which
prevents the user to change it with a preset color without deleting the
current background first.

This commit does two things:
- remove the problematic hard coded background colors;
- replace the colors that are removed by some themes by the ones that
were set in [1] (for the searchbar and text highlight snippets).

[1]: https://github.com/odoo/odoo/pull/90749

task-2824393

closes odoo/design-themes#563

Related: odoo/odoo#90749
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

theme_buzzy/views/snippets/s_text_highlight.xml

@@ -4,7 +4,7 @@
 <template id="s_text_highlight" inherit_id="website.s_text_highlight">
     <!-- Main div -->
     <xpath expr="//div[hasclass('s_text_highlight')]" position="attributes">
-        <attribute name="class" add="o_cc o_cc4" remove="bg-secondary" separator=" "/>
+        <attribute name="class" add="o_cc4" remove="o_cc3" separator=" "/>
     </xpath>
 </template>