Revert "openxr environment blend mode to alpha"

This reverts commit 22f94671e2.

src/backend/openxr/mod.rs

@@ -10,7 +10,6 @@ use anyhow::{bail, ensure};
 use glam::{Affine3A, Quat, Vec3};
 use openxr as xr;
 use vulkano::{command_buffer::CommandBufferUsage, Handle, VulkanObject};
-use xr::EnvironmentBlendMode;
 
 use crate::{
     backend::{
@@ -49,17 +48,9 @@ pub fn openxr_run(running: Arc<AtomicBool>) -> Result<(), BackendError> {
         }
     };
 
-    let environment_blend_mode = {
-        let available = xr_instance
+    let environment_blend_mode = xr_instance
         .enumerate_environment_blend_modes(system, VIEW_TYPE)
-            .unwrap();
-
-        if available.contains(&EnvironmentBlendMode::ALPHA_BLEND) {
-            EnvironmentBlendMode::ALPHA_BLEND
-        } else {
-            available[0]
-        }
-    };
+        .unwrap()[0];
     log::info!("Using environment blend mode: {:?}", environment_blend_mode);
 
     let mut app_state = {