tweak cache + revalidate fetch warning (#58505)
### What?
When using a `Request` object with fetch, we'll log a warning indicating that using the `cache` property in addition to `revalidate` is unsupported.
### Why?
`Request` sets some defaults on the request init, such as `cache: "default"`. This makes the warning confusing and there's no way to avoid it aside from switching the resource argument to be a URL string instead.
### How?
This keeps existing behavior but omits the log in the case where a request object is used and no explicit cache overrides are specified.
Fixes #58109
