mesa: remove unused texUnit local in _mesa_BindTextureUnit()

The texture unit is error-checked before this and the texUnit var
is unused, so remove it.

Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>

src/mesa/main/texobj.c

@@ -1759,19 +1759,12 @@ _mesa_BindTextureUnit(GLuint unit, GLuint texture)
 {
    GET_CURRENT_CONTEXT(ctx);
    struct gl_texture_object *texObj;
-   struct gl_texture_unit *texUnit;
 
    if (unit >= _mesa_max_tex_unit(ctx)) {
       _mesa_error(ctx, GL_INVALID_VALUE, "glBindTextureUnit(unit=%u)", unit);
       return;
    }
 
-   texUnit = _mesa_get_tex_unit(ctx, unit);
-   assert(texUnit);
-   if (!texUnit) {
-      return;
-   }
-
    if (MESA_VERBOSE & (VERBOSE_API|VERBOSE_TEXTURE))
       _mesa_debug(ctx, "glBindTextureUnit %s %d\n",
                   _mesa_enum_to_string(GL_TEXTURE0+unit), (GLint) texture);