document that "skip port" annotations interfere with tap

[cratelyn]

see linkerd/linkerd2#13976.

we provide a collection of annotations that instruct the service mesh to bypass the proxy entirely for traffic on particular ports. this has various uses, most importantly debugging, but affects tap.

when traffic bypasses the proxy, it can no longer be inspected by the proxy.

we should document that skipping ports will disable tap, as this relationship is currently implicit.