Fix Function.addEnvironment not updating on redeploy

[vimtor]

closes #6264

the diff logic was incorrect because

removing Diff entirely lets Pulumi use its default input comparison, which correctly detects when the environment changes. we are already doing something similar for the aws-function-code-updater.go

proof of it working

const api = new sst.aws.Function("MyFunction", {
  url: true,
  handler: "index.handler"
});

api.addEnvironment({
  TEST: "1234"
})

change TEST=5678 and redeploy: