Update the docs to reflect the changes for 1.13 operator

[houshengbo]

Proposed Changes

• This PR updated the docs for the 1.13 operator.

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[Cali0707]

/lgtm
/approve

[knative-prow]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: Cali0707, houshengbo

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[Cali0707]

@houshengbo do we need to backport this to release-1.13?

[houshengbo]

/cherry-pick release-1.13

[knative-prow-robot]

@houshengbo: new pull request created: #5847

In response to this:

/cherry-pick release-1.13

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[houshengbo]

yes, I just created the one for release-1.13.