mesa: remove MESA_GLSL=no_opts env option

This is confusing because is only applys to GL_ARB_vertex/fragment_program,
and because of that its also not very useful.

If someone requires this for debugging they can just make an ad-hoc
code change.

Reviewed-by: Brian Paul <brianp@vmware.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>

docs/shading.html

@@ -50,7 +50,6 @@ execution.  These are generally used for debugging.
     The filenames will be "shader_X.vert" or "shader_X.frag" where X
     the shader ID.
 <li><b>cache_info</b> - print debug information about shader cache
-<li><b>nopt</b> - disable compiler optimizations
 <li><b>opt</b> - force compiler optimizations
 <li><b>uniform</b> - print message to stdout when glUniform is called
 <li><b>nopvert</b> - force vertex shaders to be a simple shader that just transforms