Update an explaining comment for its code

The code has been updated for wgpu-0.10 (`wgpu::TextureUsage::SAMPLED`
-> `wgpu::TextureUsages::TEXTURE_BINDING`), but its comment was not
updated at the same time.

docs/beginner/tutorial5-textures/README.md

@@ -46,7 +46,7 @@ let diffuse_texture = device.create_texture(
         dimension: wgpu::TextureDimension::D2,
         // Most images are stored using sRGB so we need to reflect that here.
         format: wgpu::TextureFormat::Rgba8UnormSrgb,
-        // SAMPLED tells wgpu that we want to use this texture in shaders
+        // TEXTURE_BINDING tells wgpu that we want to use this texture in shaders
         // COPY_DST means that we want to copy data to this texture
         usage: wgpu::TextureUsages::TEXTURE_BINDING | wgpu::TextureUsages::COPY_DST,
         label: Some("diffuse_texture"),