st: Don't try to finalize the texture in st_render_texture().

st: Don't try to finalize the texture in st_render_texture().

We can't necessarily finalize the texture at this point if we're rendering
to a texture image whose format is different from the baselevel's format.
This was introduced as a fix for fbo-incomplete-texture-03 in
de414f491526610bb260c73805c81ba413388e20, but the later fix for vmware on
that testcase in 95d5c48f68b598cfa6db25f44aac52b3e11403cc made it
unnecessary.

Fixes assertion failures in util_resource_copy_region() in
KHR-GLES3.copy_tex_image_conversions.forbidden.* when trying to finalize
an R8 texture image to the RG8 texture object's pt.

Reviewed-by: Brian Paul <brianp@vmware.com>