mesa: remove ctx->Const.sRGBCapable

It always had the same value as ctx->Extensions.EXT_framebuffer_sRGB.

Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>

src/mesa/main/fbobject.c

@@ -2405,7 +2405,7 @@ _mesa_GetFramebufferAttachmentParameterivEXT(GLenum target, GLenum attachment,
                      "glGetFramebufferAttachmentParameterivEXT(pname)");
       }
       else {
-         if (ctx->Extensions.EXT_framebuffer_sRGB && ctx->Const.sRGBCapable) {
+         if (ctx->Extensions.EXT_framebuffer_sRGB) {
             *params = _mesa_get_format_color_encoding(att->Renderbuffer->Format);
          }
          else {