docs: update nvc0 state

ARB_texture_buffer_object_rgb32 has been supported for a while already.
diff --git a/docs/GL3.txt b/docs/GL3.txt
index 5261eda..755a89c 100644
--- a/docs/GL3.txt
+++ b/docs/GL3.txt
@@ -105,7 +105,7 @@
   GL_ARB_sample_shading                                DONE (i965)
   GL_ARB_shader_subroutine                             not started
   GL_ARB_tessellation_shader                           not started
-  GL_ARB_texture_buffer_object_rgb32                   DONE (i965, r600, radeonsi, softpipe)
+  GL_ARB_texture_buffer_object_rgb32                   DONE (i965, nvc0, r600, radeonsi, softpipe)
   GL_ARB_texture_cube_map_array                        DONE (i965, nv50, nvc0, r600, softpipe)
   GL_ARB_texture_gather                                DONE (i965, nv50)
   GL_ARB_transform_feedback2                           DONE (i965, nv50, nvc0, r600, radeonsi)