GPU: Remove depth24 texture format

Metal and AMD/Intel/Vulkan don't support depth24 texture formats
natively. The backends implemented fallback to use depth32f in
stead.

Recently we removed all usages of depth24 to use depth32 and the
next step is to remove the depth24 format and the workarounds in
the backend.

Note: The removal of `GPU_DATA_UINT_24_8` isn't part of this PR.

Pull Request: https://projects.blender.org/blender/blender/pulls/140659

source/blender/python/gpu/gpu_py_texture.cc

@@ -437,12 +437,10 @@ static PyObject *pygpu_texture_read(BPyGPUTexture *self)
    * So choose data_format here. */
   eGPUDataFormat best_data_format;
   switch (tex_format) {
-    case GPU_DEPTH_COMPONENT24:
     case GPU_DEPTH_COMPONENT16:
     case GPU_DEPTH_COMPONENT32F:
       best_data_format = GPU_DATA_FLOAT;
       break;
-    case GPU_DEPTH24_STENCIL8:
     case GPU_DEPTH32F_STENCIL8:
       best_data_format = GPU_DATA_UINT_24_8;
       break;