[infra] Increase the number of shards for dart2wasm to 30
[infra] Increase the number of shards for dart2wasm to 30

Change-Id: I7e985e52d01f821db9c3626eac433e7352484217
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/235221
Reviewed-by: William Hesse <a821cddceae7dc400f272e3cb1a72f400f9fed6d@google.com>

dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk,dart-lang/sdk