add a note about the default inbound interception mode

[rsalmond]

I think this is the default mode, based on this.

https://github.com/istio/istio/blob/575e7a1087351d02325cca814c2fbc9cad0f0ad7/cni/pkg/plugin/redirect.go#L36

[istio-policy-bot]

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[istio-testing]

Hi @rsalmond. Thanks for your PR.

I'm waiting for a istio member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

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[ericvn]

/ok-to-test

[rsalmond]

/release-notes-none

[ericvn]

/test release-notes