use gc_types = true in component-model-async/fused.wast

We use `Instruction::RefFunc` when generating adapters for async lifts and/or
lowers, which Winch doesn't understand, and apparently `gc_types = true` is what
tells the test infra not to use Winch.

Signed-off-by: Joel Dice <[email protected]>

Author: dicej

tests/misc_testsuite/component-model-async/fused.wast

@@ -1,5 +1,5 @@
 ;;! component_model_async = true
-;;! reference_types = true
+;;! gc_types = true
 ;;! multi_memory = true
 
 ;; async lower -> async lift