Fixup: servo#40055

Instead of applying initial scale to page. 
- An `initial-scale` should directly affect the `visualviewport.scale`as
it is layer that manages zoom factor
w3c/csswg-drafts#9004
- `initial-scale` should be considered with `device_pixel_ratio` while
calculating `layout_viewport` as per following spec gudelines.

Specs: https://www.w3.org/TR/css-viewport-1/#the-viewport

> This specification introduces a way of overriding the size of the
viewport provided by the user agent (UA). Because of this, we need to
introduce the difference between the initial viewport and the actual
viewport.
> 
> _initial viewport_
> This refers to the viewport before any UA or author styles have
overridden the viewport given by the window or viewing area of the UA.
Note that the initial viewport size will change with the size of the
window or viewing area.
> _actual viewport_
> This is the viewport you get after processing the viewport <meta> tag.


Sample Page:
[viewport_meta_with_style_2.html](https://github.com/user-attachments/files/26271786/viewport_meta_with_style_2.html)


Testing: `tests/webview.rs`: `test_viewport_meta_tag_initial_scale`

Fixes: servo#39002

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Signed-off-by: Shubham Gupta <[email protected]>