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-ui/src/theme/constants/OverlayBackground.ts

@@ -4,6 +4,6 @@ import { ThemeType } from '..';
 
 export const OVERLAY_BACKGROUND = (props: { theme: ThemeType }) => css`
   backdrop-filter: blur(12px) saturate(200%) contrast(50%) brightness(130%);
-  background: ${props.theme.background.transparent.forBackdropFilter};
+  background: ${props.theme.background.transparent.secondary};
   box-shadow: ${props.theme.boxShadow.strong};
 `;