compute shader game of life example: use R32Float instead of Rgba8Unorm

[mockersf]

Objective

• Fixes [Example] compute_shader_game_of_life crashes. #9670
• Avoid a crash in CI due to

thread 'Compute Task Pool (0)' panicked at /Users/runner/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wgpu-0.19.1/src/backend/wgpu_core.rs:3009:5:
wgpu error: Validation Error

Caused by:
    In Device::create_bind_group
    The adapter does not support read access for storages texture of format Rgba8Unorm

Solution

• Use an R32Float texture instead of an Rgba8Unorm as it's a tier 1 texture format Proposal: read-write storage textures gpuweb/gpuweb#3838 and is more supported
• This should also improve support for webgpu in the next wgpu version