[FIX] web: fix font used on the frontend when website is not installed

Before this commit, when website was not installed, the frontend used
the default bootstrap font. That font was not receiving the unicode
support Odoo provide in the backend or the frontend when website is
installed. This is probably visible on some portal pages in hebrew or
something like that, so this could back-ported in stable if found
necessary (in that case, the fix to the `o-add-unicode-support-font` in
this PR should be back-ported too).

task-2993054

closes odoo/odoo#101068

X-original-commit: f7cfcae0f0169774e0b66b8b8083005a7cd34eaa
Related: odoo/design-themes#593
Signed-off-by: Romain Derie (rde) <rde@odoo.com>
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>

addons/web/static/src/scss/bootstrap_overridden_frontend.scss

@@ -32,6 +32,8 @@ $border-width: 1px !default; // BS Default
 //
 // Font, line-height, and color for body text, headings, and more.
 
+$font-family-sans-serif: o-add-unicode-support-font($o-system-fonts) !default;
+
 $font-size-base: (14 / 16) * 1rem !default;
 
 // Inherit color for blockquote-footer, use text-muted on top of it if you want