Recently we switched from Depth24S8 to Depth32FS8. On OpenGL the read
back of depth was not working as it asked the driver to download both
the depth and stencil part of the texture. This isn't supported when using floats
and would not return any data.
This PR forces OpenGL to read back depth component when a depth/stencil
texture is used.
Pull Request: https://projects.blender.org/blender/blender/pulls/141009
00d746059e