Demand newer async-channel version

After bevyengine#6503, bevy_render uses the `send_blocking` method introduced in
async-channel 1.7, but depended only on ^1.4.

Both bevy_ecs and bevy_tasks also depends on async-channel but they
didn't use any newer features.

crates/bevy_render/Cargo.toml

@@ -76,4 +76,4 @@ basis-universal = { version = "0.2.0", optional = true }
 encase = { version = "0.4", features = ["glam"] }
 # For wgpu profiling using tracing. Use `RUST_LOG=info` to also capture the wgpu spans.
 profiling = { version = "1", features = ["profile-with-tracing"], optional = true }
-async-channel = "1.4"
+async-channel = "1.8"