[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#604

X-original-commit: 7d193e0560
Related: odoo/odoo#103123
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

theme_bistro/views/snippets/s_image_text.xml

@@ -4,7 +4,7 @@
 <template id="s_image_text" inherit_id="website.s_image_text">
     <!-- Section -->
     <xpath expr="//section" position="attributes">
-        <attribute name="class" add="pt64 pb64 bg-200" remove="pt32 pb32" separator=" "/>
+        <attribute name="class" add="pt64 pb64" remove="pt32 pb32" separator=" "/>
     </xpath>
     <!-- Image -->
     <xpath expr="//img" position="attributes">

theme_bistro/views/snippets/s_text_image.xml

@@ -4,7 +4,7 @@
 <template id="s_text_image" inherit_id="website.s_text_image">
     <!-- Section -->
     <xpath expr="//section" position="attributes">
-        <attribute name="class" add="pt80 pb80 bg-200" remove="o_cc o_cc2 pt32 pb32" separator=" "/>
+        <attribute name="class" add="pt80 pb80" remove="o_cc o_cc2 pt32 pb32" separator=" "/>
     </xpath>
     <!-- Image -->
     <xpath expr="//img" position="attributes">