nir: Drop infer_non_readable option for nir_opt_access()

Everybody sets it to true now, and the only reason for the option to
exist was to work around a bug that's now been fixed.

Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/19162>

src/compiler/nir/nir.h

@@ -5511,7 +5511,6 @@ bool nir_opt_comparison_pre(nir_shader *shader);
 
 typedef struct nir_opt_access_options {
    bool is_vulkan;
-   bool infer_non_readable;
 } nir_opt_access_options;
 
 bool nir_opt_access(nir_shader *shader, const nir_opt_access_options *options);