Delete arch hooks

They are not used anywhere.

Test: m checkbuild
Change-Id: Ice7d68b97ca894c0c4c9efc6dc55c0870a132b9c

android/mutator.go

@@ -89,7 +89,6 @@ func registerArchMutator(ctx RegisterMutatorsContext) {
 	ctx.BottomUp("os", osMutator).Parallel()
 	ctx.BottomUp("image", imageMutator).Parallel()
 	ctx.BottomUp("arch", archMutator).Parallel()
-	ctx.TopDown("arch_hooks", archHookMutator).Parallel()
 }
 
 var preDeps = []RegisterMutatorFunc{