rust: let bilge use "let ... else" "let ... else" was stabilized in 1.65.0; bumping the minimum supported Rust version means we don't need to patch it out anymore. Reviewed-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org> Reviewed-by: Zhao Liu <zhao1.liu@intel.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>