Resolver: Validate array el is not [[block]] struct

Fixed: tint:90
Change-Id: I9500a8c7fad9acf5f797dd2903217821c953acb6
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/48421
Commit-Queue: Ben Clayton <bclayton@google.com>
Auto-Submit: Ben Clayton <bclayton@google.com>
Reviewed-by: James Price <jrprice@google.com>
diff --git a/test/compute_boids.wgsl b/test/compute_boids.wgsl
index e68daae..2f168dc 100644
--- a/test/compute_boids.wgsl
+++ b/test/compute_boids.wgsl
@@ -34,7 +34,7 @@
 }
 
 // compute shader
-[[block]] struct Particle {
+struct Particle {
   pos : vec2<f32>;
   vel : vec2<f32>;
 };