fix: Embed theme not working using Embed API (#10163)

## What does this PR do?

Fixes #10187
See [Tests Done](https://www.loom.com/share/f03e0191b60143d8b45a505042dbfa11)

## Type of change
  - [x] Bug fix (non-breaking change which fixes an issue)

## How should this be tested?
- [x] Configure embed to use `dark` theme and verify that dark theme is shown on event booking page(when user has light theme set). This is failing in main
- Additional Tests for embed to avoid any new regression
	- [x] - Configure "auto" theme using embed API and see it reacts to system theme
	- [x] - Don't configure any theme and see that "light" theme is shown even when we switch system theme(Because User has configured light theme in App)
-  Tests outside embed to avoid any new regression
	- [x] - See that light theme is shown even after switching system theme
	- [x] - Now, switch the user theme to dark and see that it reflects the change. 

## Mandatory Tasks

 [x] Make sure you have self-reviewed the code. A decent size PR without self-review might be rejected.

packages/features/bookings/Booker/utils/use-brand-colors.tsx

@@ -1,5 +1,3 @@
-import { useEffect } from "react";
-
 import useGetBrandingColours from "@calcom/lib/getBrandColours";
 import useTheme from "@calcom/lib/hooks/useTheme";
 import { useCalcomTheme } from "@calcom/ui";
@@ -17,10 +15,7 @@ export const useBrandColors = ({
     lightVal: brandColor,
     darkVal: darkBrandColor,
   });
-  useCalcomTheme(brandTheme);
-  const { setTheme } = useTheme(theme);
 
-  useEffect(() => {
-    if (theme) setTheme(theme);
-  }, [setTheme, theme]);
+  useCalcomTheme(brandTheme);
+  useTheme(theme);
 };