Remove deprecated graphics/Geometry.h and graphics/conversions.h

Summary:
`react/renderer/graphics/Geometry.h` (deprecated in 2023 in favour of the individual geometry headers) and `react/renderer/graphics/conversions.h` (deprecated in favour of `react/renderer/core/graphicsConversions.h`) have both emitted a deprecation warning for several releases. Remove them. Libraries should include `<React/Graphics.h>`, or `<React/RendererCore.h>` for the conversions, instead.

Changelog:
[General][Breaking] - Remove deprecated `react/renderer/graphics/Geometry.h` and `react/renderer/graphics/conversions.h`; include `<React/Graphics.h>` or `<React/RendererCore.h>` instead

Differential Revision: D123602894

Author: j-piasecki