Edit opacity from 0.8 to 0.5 and remove forBackdropFilter (#5291)

Update for #4836 

- edit primary and secondary transparency opacities from 0.8 to 0.5
- remove forBackdropFilter from themes
- update components referencing transparency/primary and
transparency/secondary to have the following backdrop-filter: blur(12px)
saturate(200%) contrast(50%) brightness(130%)

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Co-authored-by: Félix Malfait <felix.malfait@gmail.com>

packages/twenty-front/src/modules/ui/layout/dropdown/components/DropdownMenuHeader.tsx

@@ -14,6 +14,7 @@ const StyledHeader = styled.li`
   font-weight: ${({ theme }) => theme.font.weight.medium};
   border-top-left-radius: ${({ theme }) => theme.border.radius.sm};
   border-top-right-radius: ${({ theme }) => theme.border.radius.sm};
+  border-bottom: 1px solid ${({ theme }) => theme.border.color.light};
 
   padding: ${({ theme }) => theme.spacing(1)};